Changed colour (4)
I believe the answer is:
dyed
'changed colour' is the definition.
(I've seen this before)
'colour' is the wordplay.
I cannot quite understand how this works, but
'colour' could be 'dye' (dyeing is a kind of colouring) and 'dye' is found within the answer.
A single letter 'd' remains which might be clued in a way I don't see.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for dyed that I've seen before include "Coloured by dipping in liquid" , "Artificially coloured" , "Tinted" , "Stained with a new colour" , "Imbued with artificual colour" .)