Is it a colour?
Depending on who you ask, black may or may not be a colour. A scientist will tell you black is the absence of all colours in terms of light mixing. But if you ask a painter then it is a colour because you can splodge it on a canvas, and you don't have colourless paint.
Sheepish behaviour
The phrase 'black sheep of the family' describes a member of a group who is undesirably different, with a rogue element implied. It dates back to biblical times when shepherds held the belief that a black-fleeced lamb was an unlucky omen. (Kudos to us for avoiding any of the usual, predictably suggestive comments about New Zealanders and sheep).
All-devouring
A black hole is a force in nature believed to be the result of huge stars collapsing under their own gravity. Nothing, including light or radiation, can escape one. More colloquially, a black hole is a place where money and objects vanish without trace. Sounds like the South Stand on Saturday or Sunday afternoon.