I'm a college teacher and I use red pens. Not to shame or embarrass students but because red stands out from whatever color ink they may have used. Sometimes I will use blue or green but they use those colors sometimes too. Red is pretty much the only color I haven't seen them use. I have a bunch of Pilot G2 in red but I've really come to dislike how they write. They seem to blob and skip a lot when I use them.