Agree pen needs to change colour (3,5)
I believe the answer is:
pea green
'colour' is the definition.
(I know that pea green is a type of green)
'agree pen needs to change' is the wordplay.
'needs to change' indicates an anagram.
'agree'+'pen'='agreepen'
'agreepen' with letters rearranged gives 'PEA-GREEN'.
(Other definitions for pea green that I've seen before include "The colour of podded vegetables and the Owl and the Pussycat's boat" , "Bright colour (of vegetables)" , "Vegetable shade?" , "Shade of the Owl and the Pussycat's boat" , "Colour of Owl and Pussycat's boat (Lear)" .)