Colour lacking in bottle (6)

I believe the answer is:

yellow

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

I don't understand how the rest of the clue works.

(Other definitions for yellow that I've seen before include "'Caution' colour" , "Snooker ball" , "like a coward" , "Colour of egg yolk and cowardice" , "Colour of cowardice, custard" .)

I've seen this clue in The Telegraph.

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