Colour for putting on (5)
I believe the answer is:
green
'colour' is the definition.
(I know that green is a type of colour)
'putting on' is the wordplay.
I cannot really see how this works, but
'on' could be 're' ('on' can be mean 'with reference to') and 're' is found in the answer.
The remaining letters 'gen' is a valid word which might be clued in a way I don't see.
This explanation may well be incorrect...
'for' acts as a link.
Can you help me to learn more?
(Other definitions for green that I've seen before include "Genre (anag.)" , "Envious; naive" , "Flourishing" , "Money" , "Environmentally-friendly" .)