Fun with Google NGram.

Favourite colours mentioned in books (American spelling)

Note that in 1994, purple was more often a favourite colour than yellow. Why only then? Who likes yellow?

Favourite colours mentioned in books (British spelling)

Why does nobody like purple?? It has been my favourite colour since I was at least two. My mom would have to buy new crayons because I finished all the purple, and I obviously needed that for everything.

Mention of names of colours in general: