Via Ann Althouse, here is a test to test to see how well you see shades of color. It's kind of an intensive test but takes about 10 minutes to take.
I got a 16, with 0 being a perfect score and the highest in my age category was 1520. Maybe I can get a job selling paint?
Here is the link: http://www.xrite.com/custom_page.aspx?PageID=77&Lang=en