True, and that is why I am kind of baffled by guys who will spend big money having grease crayons specially made so they can "exactly duplicate" the "correct colour" of the inspector's scribble mark on the rear axle housing (or whatever). Um...that mark was almost certainly whatever colour of crayon fell to hand. They weren't going to stop the line because they were out of a particular, specific, exact shade of yellow (or whatever).