A term used to describe one's usually
pallid appearance after a big night out. Literally, if someone says "You've got your
disco tan on", you will probably be looking rather white (usually only if you have an
Anglo-Saxon appearance, obviously) and pasty with bleary eyes after a night of
boozing and/or drugs under unnatural lighting. Essentially a slightly nicer way of saying '
You look like shit'.
See also the similar expression; '
a night on the tiles'.