Richard's red gave green in this! (6)
I believe the answer is:
indigo
'green in this' is the definition.
The answer and definition can be both human attributes as well as being singular nouns.
Perhaps you can see a link between them that I can't see?
I can't explain the rest of the clue.
(Other definitions for indigo that I've seen before include "Blue-purple colour in spectrum" , "Deep violet-blue colour" , "Blue dyestuff" , "Deep-blue dye or colour" , "Tropical plant" .)