First off Doctor, the most common colorblindnesses people have are having difficulty distinguishing green, yellow, and bright orange, red and brown, and blue to purple. I kinda having all 3 along with nearly complete coloblindness to red (almost gray to me). I think that idea with the symbols would be great tho, because in the last 2 weeks alone I'm starting to realize exactly how many people are colorblind, I've met at least 20 ppl in the game who are and at my school I've met 4 other people.
and btw, about the marking, I can't even read the markers on my map so I just try to remember what's what.
EDIT:Not to be mean to you doctor, I just noticed I kinda said this in a mean way (whoops)