Some people see colours when they look at numbers and letters, and according to this report scientists can explain why: it has to do with 'cross-activation between adjacent areas of the brain involved with processing different sensory information'. I'm in no position either to confirm or to challenge this, but it reminds me of something I've never shared with you and you'll be aching to know; which is that for as long as I can remember I've seen the days of the week as having a colour.
Monday, Wednesday, Friday and Saturday are black; Tuesday and Thursday are red; and Sunday is orange. The days are also spatially arranged, approximately so:
FridayThe week begins bottom left, on Monday.Thursday - - - Saturday
Wednesday
Tuesday - - - SundayMonday