Today I’m going to show you the best reflex sight.
In fact:
I’ve hand-tested over 20 red dot sights alone for this review.
The best part?
I’ve sorted the optics by use. So whether you’re on a budget or need the best reflex sight for your AR-15, pistol or shotgun, you’ll find it here.
Let’s dive in!
| Best Reflex Sights | Category | Price |
|---|---|---|
| Best Reflex Sight for AR-15 | $445.00 | |
| Best Reflex Sight for Pistol | $469.99 | |
| Best for the Budget | $21.99 | |
| Best Shotgun Reflex Sight | $70.00 |
Red Dot Sight vs. Reflex Sights vs. Holographics
Red dot sights work using a LED emitter that shines a beam of light onto a specially coated, slightly angled piece of glass.
The glass reflects the light from the LED onto it, creating the reticle. It offers many advantages that aren’t available with traditional iron sights.
The term “red dot sight” is a catch-all for a few types of optics, mainly reflex and holographic sights. We group these sights by how they operate. Reflex sights are reflective sights that use traditional lenses, while holographic sights utilize lasers.
Reflex Sight
The reflex red dot sight is the most popular.
It works via a small light that’s projected from the rear of the scope, which the front lens reflects back into the form of a red dot which you use to aim with.
Most reflex sights are often cheaper than holographic sights and are also available for battery-free use.
On the downside, reflex sights aren’t magnified, but you could always combine them with the best red dot magnifiers. It also comes in a wide variety of sizes and weights, meaning you can easily find a budget reflex sight to fit your firearm.
Holographic Sight
The second most popular red dot is the holographic sight, with Eotech leading the industry (Enter: EXPS 2 and 3).
It uses a powerful laser emitter to illuminate a glassed-in reticle, which is very precise, accurate, and easy to use. Holographic sights also tend to favor those with blurry vision and astigmatism.
Because of its technology, holographic sights require more battery life. That’s why it rarely lasts more than a few hundred hours. It’s a big difference when compared to 10,000+ hours of a quality reflex sight.
One of its best features is that it can still function even if the front lens is damaged. On the other hand, the most expensive red dot reflex sight on the market is still cheaper than most holographic sights.
Since the needed technology requires more internal structure and larger housings, holographic sights tend to be heavier and bulkier.
As of now, only two companies produce true holographic sights which also limits your options.
To make your life easier, I have compiled a list of the best holographic sights for you to check out.
Both reflex and holographic sights have their similarities as well as distinct differences. Choosing the best red dot sight for your specific need can mean the difference between success and failure.
How to Choose the Best Reflex Sight
With so many options on the market today, it can get overwhelming.
But don’t worry, we’re going to cover all bases: starting with how to choose the best reflex sight…
Reticle Size
A reflex sight gives you the ability to acquire and hit a target incredibly quickly.
The size of the reticle pattern can affect how quickly you can locate the dot and how much of the target it covers. These two factors have a big impact on accuracy.
The most common dot size ranges from 2 to 6 minutes-of-angle (MOA). Larger dots are ideal for speed competition, steel shooting, or if you have tired eyes. For precision shooting at medium ranges, choose a smaller dot.
If you’re unsure: 3 MOA is a popular, standard choice for target shooting and self-defense. The dot will cover 3 inches at 100 yards, 1.5 inches at 50 yards, or 6 inches at 200 yards.
Reticle Color
A reflex sight comes with a colored reticle and thanks to modern technology, there are a variety of options.
Holosun specifically designed a “gold” reticle for color-blind shooters while UTG has optics that come with 30+ different color options. But today, we’ll stick to the two most common colors: red and green.
When deciding between the two, consider your shooting environment and eye condition. If you’re in a forested area or someplace that’s dominated by green, then a green dot wouldn’t work too well. However, it’s easier on the eyes and works great for daylight use.
The red dot is highly visible at night and in low-light conditions, but people who suffer from astigmatism may see a blurred dot or experience eye strain. A popular budget reflex sight comes with the classic red dot. For more details, read my Best Red Dot Sights review.
Housing Construction
The reflex sight comes in two styles: the traditional open style and the tube or pipe style.
An open-style sight offers a wider field of view. The compact design also helps you focus on your target while maintaining situational awareness. On the other hand, it’s vulnerable to the elements.
Tube-style reflex sights look like miniature scopes and have an enclosed system. This protects it from weather conditions and accidental drops. Unfortunately, it has a more limited scope of vision than the former.
Battery Life
The battery life is a crucial aspect since no dot is visible if you run out of power.
Normally, a reflex sight uses LEDs. That’s why a single battery can last 10,000+ hours. Take note, your mileage will vary depending on your brightness setting.
Some reflex sights have auto-on/off features that are driven by motion sensors, allowing it to always stay on and ready for use while conserving battery life.
Those sights are typically more expensive but extremely reliable.
Durability and Weight
A reliable red dot reflex sight should be water-proof, fog-proof, and shock-proof. It should also withstand high recoil rounds, and be durable but lightweight.
Lastly, always buy a product with a good warranty. Not all manufacturers provide coverage or excellent customer service, so make sure you check!
Choosing one that works best for you can be tricky – and finding one that fits in your budget can be trickier! Therefore, I’ve compared the best reflex sights and listed them below.
The Best Reflex Sights
If you’re pressed on time, here’s a quick list of the best reflex sights:
- Aimpoint Pro: Best Reflex Sight for AR-15
- Trijicon RMR Type 2 RM06: Best Reflex Sight for Pistol
- Bushnell TRS-25: Best for the Budget
- Vortex Venom: Best Shotgun Reflex Sight
1. Aimpoint Pro: Best Reflex Sight for AR-15
The Aimpoint PRO is the best reflex sight for the AR-15.
- Absolute co-witness with iron sights (with the supplied spacer installed)
- Features 2 MOA red dot for accurate target engagement
- Includes front and rear plastic flip cap lens covers
This patrol rifle optic is widely known for its impressive features and reasonable price point.In fact, it’s actively being used by the military, law enforcement, and armed authorities alike.
Glass Clarity & Reticle Patterns
The Aimpoint Pro’s glass is clear and crisp.
It comes with a slight blue tint for enhanced contrast, and I’ve experienced no distortion whatsoever, so no complaints there.
It features a threaded front lens opening which, get this: allows you to screw on another anti-reflective device. The Aimpoint Pro comes with a 2 MOA dot with ten brightness settings: 6 daylight and 4 night settings.
This red dot sight is also compatible with all generations of night vision devices. As awesome as the Aimpoint PRO is, the red dot sight can be less favorable for individuals with astigmatism.
In that case, you’d want to look at a holographic reflex sight like the Holosun HS510C.
Eye Relief & Eye Box
The Aimpoint Pro has unlimited eye relief.
The eye box is a bit smaller compared to other reflex sights but it has a wide field of view. The Aimpoint Pro can be co-witnessed with iron sights and it comes with an extra spacer.
In fact: The red dot perfectly lined up with my AR’s iron sight. I was able to zero within the first ten shots at 50 yards. 500 rounds later, I was still shooting dead center without issues.
Durability and Weight
The Aimpoint Pro is extremely durable.
Thanks to its anodized aluminum construction, it can withstand heavy rain, fog, and is completely waterproof up to 150 feet.
Additionally, the single CR2032 battery of the Aimpoint Pro is rated to last 30,000 hours (over 3 years) of constant operation.
On that note: I’ve used mine for almost two years now, and I haven’t swapped batteries yet.
The Aimpoint Pro is 3.2 inches tall, 5.4 inches long, and weighs about 12.7 oz with the spacer. This optic is not as lightweight as other red dots, but its design works best on full-sized rifles.
Elevation & Windage Knobs
The elevation and windage knobs are robust and tactile.
They’re easy to tighten or loosen, even with gloves on. Plus: they have an audible click and can be easily reset back to your desired setting.
Parallax & Magnification
The Aimpoint pro features a 1x magnification.
It was easy to shoot with both eyes open, and the red dot sight was parallax-free.
You can also use the Aimpoint Pro with any magnifier of your choice. I used both Aimpoint’s 3X Magnifier
- 3X magnification.
- Variable (-2 to +2) dioptric setting.
- 3X-C Magnifier only – NO MOUNT INCLUDED.
and Vortex Optics VMX-3T Magnifier with Built-in Flip Mount and it improved my long-range accuracy tremendously.
- The VMX-3T Magnifier and Flip Mount combo adds a 3x magnification to your rifle's red dot sight. Simple, fast, and effective, the push button design engages and disengages the flip mount allowing the...
- The lens are fully multi-coated maximizing resolution, light gathering capability, and color fidelity. Eye Relief-2.2 inches. Field of View-38.2 feet/100 yards
- The VMX-3T does not require any special sight-in. The dot centering screws can be used to help center your red dot image in the VMX-3T's field of view.
Mounting & Rings
The Aimpoint Pro comes with a standard AR-15 riser (which is removable) and a dual-height, torque-perfect QRP2 mount.
It took me a total of 15 minutes to install everything.
Also, the box includes flip-up lens covers – the front is solid and the rear is transparent. This allows you to shoot with the lens caps closed and both eyes open in case of an emergency.
Is the Aimpoint PRO worth it?
If you’re looking for a high quality reflex sight that won’t fail on you or your AR-15, I highly recommend the Aimpoint Pro.
Why? It’s got:
- Pinpoint accuracy
- Clear and crisp lens
- 30,000-hour battery life
- Easy installation and removal
- Excellent durability and construction
On top of that, the reflex sight is covered by Aimpoint’s 10-year warranty. If it ever breaks, their excellent customer service will repair or replace it for free.
Overall, the Aimpoint Pro is one of the best scopes for the AR-15. You definitely won’t be disappointed with the quality and reliability you’re paying for.
- Absolute co-witness with iron sights (with the supplied spacer installed)
- Features 2 MOA red dot for accurate target engagement
- Includes front and rear plastic flip cap lens covers
2. Trijicon RMR Type 2 RM06: Best Reflex Sight for Pistol
The Trijicon RMR Type 2 is the best reflex sight for the pistol.
- 3.25 MOA ADJUSTABLE LED RMR: Features an automatic brightness mode and easy push buttons for eight adjustable brightness settings including 2 nv and 1 Super bright
- DEPENDABLE ELECTRONIC DESIGN: Ruggedized Battery contacts and electronics ensure performance and survivability in harsh environments
- UNIQUE PATENTED HOUSING SHAPE: Military-grade aluminum alloy forged housing shape diverts force of impact away from the lens, greatly increasing its durability
Whenever I’m looking for a top-tier optic, you can always find me browsing at Trijicon. Compared to a lot of contenders, this red dot sight has proven to be extremely accurate, durable, and reliable.
This is why the Trijicon RMR Type 2 is one of the best pistol red dot sights…
Glass Clarity & Reticle Patterns
The Trijicon RMR Type 2 glass is super clear and bright.
This reflex sight comes with a 3.25 MOA red dot, perfect for shooting precisely without covering too much of my target.
The RMR Type 2 has easy-to-use plus and minus buttons for quick illumination adjustments. I can also manually adjust its brightness, up to eight different settings. All the controls are side-mounted for easy access.
I also tried switching to the auto-adjust mode, and it worked perfectly. It detected the ambient light and gave me a red dot that suited my shooting conditions.
On the other hand, I was hoping the Trijicon RMR Type 2 would come with “shake awake” motion sensing technology (like the Holosun HE508T-X2). This would’ve been a great addition.
But, it’s not a big deal considering this reflex sight has a long list of impressive features.
Eye Relief & Eye Box
The RMR Type 2 has unlimited eye relief.
The eye box is forgiving and has a large field of view. You can easily achieve quick target acquisition with both eyes open, perfect for enabling rapid engagement.
Durability and Weight
The Trijicon RMR Type 2 is lightweight yet durable.
The RMR Type 2 is waterproof and fog proof. Plus: it’s proven to withstand the stresses associated with recoil on high-power firearms.
I’ve personally done multiple drop tests and one-handed reloads on this optic and found no problems. The Trijicon RMR Type 2 is equipped with long-lasting battery life.
You can expect up to four years of use from its single CR2032 battery. I recommend replacing it every year, though.
The drawback: The battery compartment is on the bottom of the reflex sight…so you have to unmount and re-zero when you swap them out.
If that troubles you, a red dot sight with a top-loading battery option like the Burris Fastfire III is a great alternative.
Elevation & Windage Knobs
The RMR Type 2’s knobs are solid with audible clicks.
Windage and elevation changes are made with 1.0 MOA clicks over a 150 MOA range. I was able to zero within the first 15 rounds.
After firing over 1,000 rounds, I can personally confirm there were no flickers or loss of zero.
Parallax & Magnification
The RMR Type 2 sports a 1x magnification.
It’s factory adjusted to be parallax-free at approximately 100 yards. This setup works very well for a pistol.
Mountings
The RMR Type 2 doesn’t come with mountings.
However, there’s a wide selection you can purchase online. I used the Trijicon AC32064 RMR mounting kit—not included—which comes with a gasket that mounts between the unit and the mounting plate.
- This kit includes the sealing plate and proper screws needed to mount an RMR on the MOS and Springfield OSP slide
- Fits G17 Gen4 MOS, G19 Gen4 MOS, G34 Gen4 MOS , G35 Gen4 MOS, G40 Gen4 MOS, G41 Gen4 MOS, and Springfield OSP
- The AC32064 kit includes: RMR Sealing Plate, two RMR Screws (short) and Hex Key
At least, that’s what I used to marry the Type 2 to my Glock 17 MOS. Depending on your slide, I recommend buying the Mount Sealing Plate to avoid water getting in. It gives your pistol a perfect seal with the reflex sight.
- Allows the rmr to be submerged up to 66ft for up to 1 hour without leaks
- Compatible with all Trijicon manufactured rmr pistol mounts
- Made from stainless steel
Is the Trijicon RMR Type 2 worth it?
If you’re looking to mount a professional-grade reflex sight on your AR pistol, get the Trijicon RMR Type 2.
Here’s why:
- Multi-coated lens
- Long-lasting battery
- Night vision compatible
- Low profile and lightweight
- Manual/Automatic brightness mode
Also, this red dot reflex sight comes with Trijicon’s Limited-Lifetime Warranty. You won’t need to worry if you require repairs or a replacement.
If the red dot reflex sight on my pistol could be a matter of safety or survival, I’d pick the Trijicon RMR Type 2 reflex sight in a heartbeat.
But if you’re looking for the best budget reflex sights alternative, I have a detailed comparison on the Burris Fastfire 3 vs Trijicon RMR. Highly recommend checking that out!
- 3.25 MOA ADJUSTABLE LED RMR: Features an automatic brightness mode and easy push buttons for eight adjustable brightness settings including 2 nv and 1 Super bright
- DEPENDABLE ELECTRONIC DESIGN: Ruggedized Battery contacts and electronics ensure performance and survivability in harsh environments
- UNIQUE PATENTED HOUSING SHAPE: Military-grade aluminum alloy forged housing shape diverts force of impact away from the lens, greatly increasing its durability
3. Bushnell TRS-25: Best for the Budget
The Bushnell TRS-25 is the best reflex sight for your money.
- Matte black featuring a 3 MOA Dot reticle with 11 brightness settings; Mounts easily on most picatinny rails and is compatible with pistols, shotguns, rifles and muzzleloaders.Adjustment Range : 70+...
- Waterproof construction: O ring sealed optics stay dry inside, even when totally immersed in water. Parallax - 50
- Shockproof construction: Built to withstand bumps, bangs, drops and the rough and tumble environment of the field
It costs less than $100 and performs as well as optics twice its price. In fact, it’s got 12,000 reviews on Amazon, with customers raving about this affordable red dot. And I agree with them.
Glass Clarity & Reticle Patterns
The Bushnell TRS-25 provides superb optical clarity.
It features amber-bright lens coating that prevents glare and improves light transmission. Amber-coated optics will help you distinguish what you are aiming at, be it a brown tree or brown critter. Super helpful on hunting trips!
The TRS-25 is equipped with 11 brightness settings, illuminating the 3 MOA dot reticle inside to better help you with target acquisition.
I did notice that the dot intensity tends to get a bit blurry when the setting is high. It’s not ideal but it’s acceptable at this price point.
Eye Relief & Eye Box
The Bushnell TRS- 25 sight sports unlimited eye relief.
I’m able to comfortably shoot with both eyes open. It also comes with a wide field of view and is parallax-free.
Durability and Weight
The Bushnell TRS-25 is both durable and lightweight.
The aluminum housing is filled with dry nitrogen gas and sealed with O-rings which makes it fog-proof, waterproof, and shockproof. Also, I have put this optic through the wringer.
If I were to drop it from 5 feet, the glass would probably crack but keep in mind, it’s a low-cost red dot. With regular use, it passes the torture test. On the downside: the battery life isn’t so great.
Bushnell says it comes with 5,000 hours of battery life on the medium setting, but I’ve been swapping out batteries every year. An auto-shutoff feature would’ve been ideal with the low battery life.
Still, not bad for a $70 optic!
Elevation & Windage Knobs
The elevation and windage knobs have an audible click.
You will need a screwdriver or coin to turn the adjustments. Every click on the dials equals 0.5 MOA. After 10 rounds, I was zeroed in.
I’ve tested it using AR-15 assault-style rifles and even shotguns, and it held the zero throughout.
Parallax & Magnification
The Bushnell TRS-25 comes with 1X magnification.
If you want to add some magnification, the UTG 3x Magnifier is the way to go. I own one and it’s affordable and reliable. It’s also parallax-free.
- Broadband Multi-coated Lens to Provide Crystal Clear 3X Image, Wide Field of View - 30% Bigger Than Comparable Models from Other Brands.Compatible Rail-Picatinny/Weaver.
- Windage/Elevation Adjustability for Optimum View Centering. Refer user manual for list of compatible manuals
- 42mm Center Height for Most Common Dot Sight Combination, Innovative Flip-to-Side Mechanism for Quick Transition between 1X and 3X Image.Objective Diameter:25mm;Field of View @ 100 yards:45'
No matter where my eye was positioned, the dot didn’t move.
Mountings
The Bushnell-TRS 25 is a pretty versatile accessory that can be easily mounted on any Picatinny rail system or weaver style.
However, you may need a riser mount if you are shooting an AR-type rifle. I personally recommend the UTG 1″ Riser.
- New Gen. Riser Mount for Rifles with Picatinny/Weaver Rail
- 1.6" Long Picatinny Rail with 3 Slots
- Side Plate with Spring Tension for Quick Easy Installation
For absolute co-witness, the UTG .83″ Riser is my go-to.
- New Gen. riser mount for rifles with Picatinny/Weaver rail
- 1 Picatinny rail with 3 slots
- Side plate with spring tension for quick and easy installation
Is the Bushnell TRS-25 worth it?
If you’re looking to get an affordable reflex sight that does it all, get Bushnell TRS-25.
Why? It’s got…
- Clear reticle
- Affordable price tag
- Multi-coating on lenses
- Easy to mount and easy to detach
- Shockproof, fog-proof and water-proof
Plus, the TRS-25 is protected by Bushnell’s Lifetime Warranty. If the sight arrives with a defect, they will either replace or repair it. If you’re interested in this red dot, you can find more information on my in- depth review of the Bushnell TRS-25.
- Matte black featuring a 3 MOA Dot reticle with 11 brightness settings; Mounts easily on most picatinny rails and is compatible with pistols, shotguns, rifles and muzzleloaders.Adjustment Range : 70+...
- Waterproof construction: O ring sealed optics stay dry inside, even when totally immersed in water. Parallax - 50
- Shockproof construction: Built to withstand bumps, bangs, drops and the rough and tumble environment of the field
4. Vortex Venom: Best Shotgun Reflex Sight
The Vortex Venom is the best shotgun reflex sight.
Not only is it affordable, but it’s packed with amazing features. In fact, I’ve used it on a wide variety of hunting applications including casual target shooting and I loved it.
Glass Clarity & Reticle Patterns
The Vortex optics glass is clean, crisp, and bright.
This optic comes in either a 3-MOA or 6-MOA red dot reticle. I prefer the 3-MOA dot for hunting. The precise dot permits fine-tuning for true target acquisition.
In my opinion, the 6-MOA dot is too big, definitely for shots over 40 yards because it just covers too much of the vitals. But this is also a personal preference.
The Venom has 10 brightness settings in total and offers manual or automatic brightness adjustment.
There’s one thing I’m not a fan of: When you aim from a dark place into a brightly sunlit area, the dot tends to wash out as the light sensor sees a low level of light and automatically adjusts the brightness down.
For battery preservation, the durable sight is designed with an automatic shutoff function after 14 hours. So far, I’m happy with that trade-off.
Eye Relief & Eye Box
As a red dot sight, the Venom comes with unlimited eye relief.
It also has an ultra-forgiving eye box and shooting with both eyes open was a breeze. If you can see the red dot, you’ll hit your target.
Durability and Weight
Vortex’s Venom sight is inexpensive, but it’s compact and robust.
It’s made of aircraft-grade aluminum and is nitrogen purged, making it waterproof and shockproof. The sealed O-rings prevent dust, debris, and moisture from entering the device.
It withstood every shake, rattle, and roll I threw at it. The Vortex Venom is rated between 150 (at the brightest setting) to 30,000 hours (at the lowest setting) of battery life.
With its top-mounted battery compartment, there’s no need to remove the optic to replace the CR 1632 battery.
But what if the battery life isn’t enough for you? Check out its cousins: the Sparc 2 and Strikefire 2.
Elevation & Windage Knobs
The knobs are easily adjustable with audibly crisp 1 MOA clicks.
I was able to zero in the scope within 5 minutes. Even after 1500 rounds, it still held zero.
Parallax & Magnification
The Vortex optics don’t come with any magnification- as is the standard with a reflex red dot.
This is ideal for short-range shooting. But, if you want to add 100 yards, I recommend the Vortex VMX 3T Magnifier.
- The VMX-3T Magnifier and Flip Mount combo adds a 3x magnification to your rifle's red dot sight. Simple, fast, and effective, the push button design engages and disengages the flip mount allowing the...
- The lens are fully multi-coated maximizing resolution, light gathering capability, and color fidelity. Eye Relief-2.2 inches. Field of View-38.2 feet/100 yards
- The VMX-3T does not require any special sight-in. The dot centering screws can be used to help center your red dot image in the VMX-3T's field of view.
Although the Venom is labeled as “parallax free”, there is slight parallax. But it makes a negligible difference in performance.
Mountings
The Vortex optics will directly attach to any shotgun with a Picatinny/Weaver Rail.
The box also includes a T-15 Torx wrench, Rain cover, Lens cloth, Mounting screws, one CR 1632 battery, and a screwdriver.
Is the Vortex Venom worth it?
If you’re in search of a low-profile yet rugged reflex sight for your shotgun, the Vortex Venom is it.
Why? It’s got…
- Clear glass
- Crisp 3- or 6- MOA dot
- Auto brightness setting
- Long-lasting battery life
- Waterproof, fog-proof, and shockproof
And to top it all off, if you’re worried about it breaking, Vortex optics’ Lifetime VIP warranty has you covered: they will repair or replace it without charge, no receipts required.
Overall, I consider the Vortex Venom to be a bang for your buck.
If you’re looking for another great option for your shotgun, I highly recommend checking out my Vortex Sparc AR vs Sig Romeo 5 review!
Now It’s Your Turn
I hope you enjoyed my Best Reflex Sights guide.
Now I want to turn it over to you: Which reflex sight will you pick for your AR-15, pistol or shotgun? Or perhaps you already have one and would like to share your thoughts.
Either way, let me know by leaving a quick comment down below.
FAQ:
The country’s military units commonly use the Aimpoint and EOTech red dot sights, just to name a few things The military requires perfect accuracy and precision concerning as they can’t allow themselves to miss their target, therefore the need for the high-quality and top-tier red dot sights.
In general, a good reflex sight is lightweight yet robust. You also want to look for quality glass that has a clear projection of light, regardless of the time you are hunting or the location. An added important factor would be battery life. You don’t want to end up with a dead battery in the middle of a hunt! MOA dot size and reticle color can be personal preferences. These are a few considerations when looking for a good reflex sight.
Red dot sights work great at night. Since they are illuminated, you aren’t stuck with black iron sights on a dark background. In fact, there are even models that are compatible with night vision devices (NVDs), like the Aimpoint Pro. You can also use a laser sight when it’s night but bear in mind, you might scare off animals with it.
Your eyes might be your own worst enemy when owning a red dot with astigmatism. You can get contact lenses, glasses, and even refractive surgeries. If this isn’t on the table, buying a high-quality red dot with green illumination or investing in a holographic sight may help to alleviate the blurry effect of astigmatism.
Would like to see something written that covers use of hand cannons like the S&W 350 Legend, 460 S&W, or even the S&W 500. The article should show the revolver being used in hunting anything from hogs, to dangerous animals.
I prefer that the article involves not only Red Dot sights, but the option of using a Green Dot for those of us that have trouble see the Red Dot due to color perception/color blindness problems.