Turns red, maybe (4)
I believe the answer is:
dyes
'turns red maybe' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for dyes that I've seen before include "Colouring materials" , "Colour" , "Many a pigment" , "turns green, possibly" , "Substances for staining or colouring" .)