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 an anagram.
'staple' is an anagram of '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" .)