I also have colors associated to all kind of concepts: time periods, numbers, letters, tastes, music genres, even people.

E.g., my timeline is a ladder, where early universe era is dark blue, dinosaurs time is bright green, human prehistory is brown, 0 AD is yellow/orange and medieval times are light blue. Modern to contemporary era is detailed to a finer scale, e.g. the seventies are purple, the eighties are azure, nineties are yellow and 00s are white.

However, this is a very general thing: each time I recall some concept from my mind, my inner google also returns the color associated with it.