Get a man to change colour (7)
I believe the answer is:
magenta
'colour' is the definition.
(magenta is a shade of purple)
'get a man to change' is the wordplay.
'to change' indicates anagramming the letters.
'get'+'a'+'man'='getaman'
'getaman' with letters rearranged gives 'MAGENTA'.
(Other definitions for magenta that I've seen before include "Colourful" , "Light mauvish-crimson" , "French victory" , "Deep purplish red" , "Colour named after a bloody 1859 battle in Italy" .)