Crossword Genius

An argument about colour (4)

Ross

I believe the answer is:

blue

I'm a little stuck... Click here to teach me more about this clue!

'colour' is the definition.
(blue is a kind of colour)

I can't explain the remainder of the clue.

Can you help me to learn more?

(Other definitions for blue that I've seen before include "Colour; obscene" , "This movie is X-rated" , "Red-headed Australian" , "very cold" , "Varsity sportsman" .)

I've seen this clue in the Sydney Morning Herald.
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