I am not a trained physician (you would be surprised how many times I have been asked about that), so take this post for what you will.
I was cruising around the Internet, as I am wont to do from time to time, and I came across this page that lists a number of different color blindness tests. As we know, I am slightly color blind (though I suppose I don't REALLY know how color blind I am). I am afflicted with red/green color blindness, which is the most common form of color blindness (ah, I'm so common). The image to the right comes from the Ishihara color test and is a quick way to see if you have red/green color blindness. Most people should see a '5' in the dots, whilst people like me clearly see a '2' (which, in fact I do).
Perhaps this explains why I can hardly dress myself.