According to Wikipedia there are an estimated 10.5 million American men who are red green color blind. I am one of them. I discovered this many years ago and rarely think about it as to me it is normal. However, I have discovered that those around me are endlessly fascinated with it—especially designers. So, to you I provide this public service message on color blindness.
First a little bit of myth busting. Red and green do not appear gray to me, perhaps less bright then you are used to but not gray. Second, color blindness does not give me superpowers. I cannot magically see through red and green objects and describe what is behind them. (It would be nice at times though (-: .)
Now for the really fun part. This is a series of images created with Vischeck that appear the same to me. Really they do, at most one is a very tiny shade lighter. So to the designers out there, please remember me and my millions of friends before you output something that I can't read.