Staple changed colour (6)
I believe the answer is:
pastel
'colour' is the definition.
(pastel is a kind of colour)
'staple changed' is the wordplay.
'changed' indicates anagramming the letters.
'staple' with letters rearranged gives 'PASTEL'.
(Other definitions for pastel that I've seen before include "Type of crayon" , "pigments mixed with gum" , "Of a colour, subtle" , "Staple (anag)" , "A light delicate shade of colour" .)