If you are colorblind you probably already know it. What you may not know is that there is a company that makes glasses and sunglasses that will correct it in about 75% of people. Their website (http://enchroma.com/) can answer a lot more of your questions than I can here, so if you or someone you knows is colorblind you may want to direct them there. 1 in 12 men are colorblind (1 in 200 women), so chances are you know someone.
Briefly it works by filtering the wavelengths of light that enter the eye. Lots of explanation on the website, plus testimonials including videos of people breaking into tears as they see real color for the first time. The glasses are expensive, but I think most colorblind people would find it worth it, AND there is a 60 day money back guarantee.
There is a section on the website where you can test yourself and see what kind of colorblindness you have. Here is a copy of one of them. In the picture below, both sides look absolutely, 100% the same. No variance at all. None.
No difference to me - not even the most subtle shade of difference. My wife just shakes her head in pity and says there are big differences. So, I ordered a pair (something like 350 bucks), hands trembling with anticipation I tried them on. Nothing. Wore them for a couple of hours on more than one occasion. Still nothing. That's the bad news. The good news is that good to their word I got all of my money back.
Anyway, I wanted to pass that along. I am back to using index cards to tell all of the flies in my box apart and asking my wife if the light is still red or has turned to green on the battery charger. Sigh. But hopefully these will work for one of you or someone you know.