There are certain colors which I tend to identify as green which other people assure me are gray. I didn't realize this until I got into an argument with a friend about her sofa. Now I see these colors in a weird superposition of green and gray. (I see some things as unambiguously gray, and correctly identify actual green things reliably.) I'm not sure if this is an actual vision issue (it doesn't seem to be a form of colorblindness) or what.