Go-ahead colour (5)

I believe the answer is:

green

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This clue might be a double definition.

'go-ahead' is the first definition.
The answer and definition can be both human attributes as well as being singular nouns.
Maybe they are linked in a way I don't understand?

'colour' is the second definition.
(I know that Green is a type of colour)

Can you help me to learn more?

(Other definitions for green that I've seen before include "Unripe; environmentalist" , "Genre (anag.)" , "Eco-friendly" , "Not yet ripe" , "Flourishing" .)

I've seen this clue in The Globe and Mail.

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