It's colourful, albeit dull (5)

I believe the answer is:

khaki

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'dull' is the definition.
(khaki is a dull colour)

I cannot understand how the remainder of the clue works.

(Other definitions for khaki that I've seen before include "Dull yellowish-brown" , "Dull brownish" , "strong fabric" , "Dullish brown colour" , "Military uniform cloth - colour" .)

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