A faster colour than red? (5)

I believe the answer is:

green

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'red?' is the definition.
The answer and definition can be both human attributes as well as being singular nouns.
Perhaps there's a link between them I don't understand?

I can't explain the remainder of the clue.

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(Other definitions for green that I've seen before include "Not yet ripe" , "Ecologically correct" , "Genre (anag.)" , "Eco-friendly" , "The colour of envy" .)

I've seen this clue in the Evening Standard.

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