ALTOk so Martin design update I know what I want him to look like from season 4 onwards!
I am a big fan of Martin with a beard, especially late-game (cause then he and Jon get to be matching), I think it can do a lot for representing his character. In the early seasons he’s making himself small, he wants to be underestimated, and I think that a clean-shaven slightly boyish look would really contribute to that + add to the fun balancing act of both seeming older than he is and less competent than he is at the same time. So if you establish that look and then give him a beard at the beginning of season 4 you get to communicate the time jump AND very quickly show that his persona has drastically changed.
Anyways HAIR! Still don’t know about color (thinking maybe a dirty blonde or like, mousy brown…? Something that doesn’t stand out very much but heavily contrasts Jon’s color palette, which is heavy on dark greens and browns.) I really like the idea of his hair having a permanent sort of damp look from the fog. Sometimes, when you look over from the other side of the room, his hair is ever so gently swaying in a breeze you can’t feel, like he’s somewhere outside, far, far away.