A shade too revolutionary for some (3)

I believe the answer is:

red

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'a shade' is the definition.
(red is a colour or shade)

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

(Other definitions for red that I've seen before include "eg Cardinal" , "Merchant flag" , "- Cross; - carpet" , "Very angry, seeing this" , "Ruby" .)

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

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