Plates changed colour (6)
I believe the answer is:
pastel
'colour' is the definition.
(pastel is a kind of colour)
'plates changed' is the wordplay.
'changed' is an anagram indicator.
'plates' with letters rearranged gives 'PASTEL'.
(Other definitions for pastel that I've seen before include "Crayon - of soft shades" , "Pleats of a light colour" , "pigments mixed with gum" , "Crayon used in art" , "Delicate colour found in plates" .)