Skin tone, wigs and contacts have been on my mind lately too.
help disguise explicitly says that players need to disguise their character from other players.
DISGUISE FROM THE PLAYER & THE CHARACTER
You should strive to not only disguise yourself from the other character, but also the other player! If they can't OOCly guess who you are via meta cues such as recognizing your characters clothing, you have won half the battle.
The obvious nature of contacts and wigs are MAJOR meta clues. They are so obvious that I do not bother to use them when trying to deceive other players. I (opinion of one here) feel that they are only useful for interacting with NPCs / staff puppets.
We all try our best to be mature and respect disguises, even obvious ones. But the reality is that very few players are going to put their characters in the position of losing when they're being setup by a character with obvious disguise items.