Learned about colour many years ago (5,3)
I believe the answer is:
stone age
'many years ago' is the definition.
'learned about colour' is the wordplay.
'learned' becomes 'sage' (I've seen this before).
'about' means one lot of letters goes inside another.
'colour' becomes 'tone' (tone is a kind of colour**).
'sage' going around 'tone' is 'STONE-AGE'.
(Other definitions for stone age that I've seen before include "time long ago" , "Old time" , "Goat seen (anag.)" , "Go, senate to ancient era before metal was discovered" , "Neolithic" .)