Cum starts out as clear for most guys, since they can't produce enough semen to make it white. (although, it's NOT called precum)
Then it'll turn white. Whatever you have, clear or white, if you clean up with a tissue and notice that it has a yellowish tint, don't worry about it! It just has some urine mixed in with it. It'll clear out of your urethra after a few jacking sessions.
It shouldn't be any color that resembles red. I.e., red, brown, or orange (ew