Colours! (or "colors" for you Americans)
I've seen school lockers that were brown, red, blue and black - but in my mind's eye, they are always green.
I also associate colours with the days of the week: Monday is blue, Tuesday is red, Wednesday is green, Thursday is brown, Friday is black, Saturday is orange, and Sunday is yellow. I've seen the days of the week this way as long as I can remember.
Anyone else have any other strange colour associations?