I’ve always believed that web site accessibility depends on an understanding of accessibility issues — not on technical issues. Obviously, knowing the technical side of web site construction and how it impacts accessibility is very important. Some decisions are fundamentally technical, but a huge part of web site accessibility is purely visible — and just understanding accessibility issues will make a huge difference.

To that end, here are a few quick comments about color blindness. Color blindness (or color perception deficiency) is an issue for approximately 1 in 12 people, mostly men. However, color perception problems are not always very effectively diagnosed, so these numbers could be low.

Color blindness is an inability to see certain colors.

Color blindness is really a misnomer. People with various types of color blindness are better described as being color vision deficient: it’s an inability to distinguish colors, not an inability to see color. People at the furthest limits of color deficiency, however, may have such an extreme inability to discern colors that this can be a fairly accurate description.

Individuals with color vision deficiencies can’t see red.

Well, no. Assuming we’re discussing Protanopic or Deuteranopic color blindness, in which the individual is missing either the red or green sensitive cones, the actual problem is that they may not be able to distinguish the color red. The color isn’t readily differentiated from other hues of the same shade or tint. Red perception deficiency is certainly the most common type of color vision deficiency, but it’s certainly not true of all individuals with poor color vision.

You have normal color vision

Not really. In fact, color perception is a spectrum for all of us. What’s commonly referred to as color blindness is actually only the portion of that spectrum which is considered anomalous — where the ability to perceive color begins to impinge on normal interactions with the world. Having “normal” color vision simply means that you don’t generally experience problems because of your color vision. You may well still fail an Ishihara test.

Color perception deficiencies are inconvenient, but don’t pose any serious problems

Particularly in our modern, technological society, color perception is a critical part of comprehending the world around you. From LED indicators which blink red, green, or yellow; to weather maps which a spectrum from red to green indicating storm severity; to knowing what color a traffic signal is showing if you’re in a location with a different signal orientation than what you’re familiar with. Outside of technology, color deficiencies can impact recognizing that you’re developing a severe sunburn or knowing whether you’ve actually cooked that hamburger enough to be safe.

People with Color Perception Deficiency have better Night Vision

Actually, I couldn’t definitely verify this one way or the other. There are a number of claims that this is true, but the reasoning is highly variable and not particularly evidence-based. It’s possible that certain types of color perception deficiency may give people better night vision, but it’s also possible that since some types of color perception deficiencies cause people to be photosensitive, those people may feel like their night vision is better, simply because it’s much better than what they’re accustomed to. Regardless, any evidence which is reasonably definitive would be appreciated.

Additional Resources

• Vision Simulator
• Colour Blindness on the Web isn’t a big deal

Whenever somebody tells me that they really don’t see the point in doing usability testing on their web site, I can’t help myself from asking why. Let’s be honest here — what’s a really good reason for skipping usability testing? The first thing that comes to my mind, of course, is because you’ve just finished a major usability review. I can understand wanting to give it a skip if you’ve just gone through the usability testing process!

But, surprisingly, that’s not the response I actually hear from people. Actually, the most common reasons are very simple:

1. I’ve never had a problem with it
2. Nobody’s every complained about a problem

Unfortunately, both of these justifications are problematic. They really aren’t a good reason for passing on usability. See, usability isn’t just about whether or not something worked; it’s also about what happens when a process doesn’t work out. It’s not about whether you made it through the process, it’s about how easy it is to make it through process. You’re pretty well guaranteed to be out of the running in testing your web site — because you actually know how your web site is supposed to work.

If you know that a field takes a particular data format – say, a five-digit postal code – then you’re going to tend to provide what you know the web site wants. It’s what happens when you don’t already know the system which is more educational.

This is certainly a frustrating aspect to usability – no arguments there. But you can’t escape it: if you have inside knowledge about a system, you’re just the wrong person to test it. Obviously, this means that problems that other users have are an important element to pay attention to.

However, a lack of reported problems is not at all the same as not having problems.

Nobody’s ever complained about a problem with your web site? That’s not a certainty of any sort. It could be a different kind of issue — rather than having problems which are very clear cut, such as an inability to enter an international address, you may be experiencing time-out frustrations or issues with a particular payment type being rejected. Or perhaps the problem is actually with the ability to report problems — maybe you haven’t provided an obvious means for people to contact you. Perhaps there’s actually a problem with your contact method itself — negative evidence is essentially worthless. All you can conclude from an absense of complaints is that nobody has delivered a complaint to you. You don’t know that they didn’t try, and you don’t know that they didn’t have a problem.

And finally, having a problem isn’t exactly what usability is trying to fix.

Your users may not be having any problems — they don’t have anything concrete to complain about. However, because your purchase process is onerous, a large percentage of those who begin the purchase fail to complete it. They may not have had an actual problem — they just decided that using your web site was too much work.

Maybe they’re just lazy — but if you’ve got lazy prospects, your site needs to work harder at keeping them around. Don’t let your web site slack off.