Boofhead! Diamonds a greenish colour? (4)

I believe the answer is:

bice

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'a greenish colour?' is the definition.
The definition suggests a singular noun which matches the answer.

'boofhead diamonds' is the wordplay.
'boofhead' becomes 'b' (head letter of 'boof').
'diamonds' becomes 'ice' (slang term for diamonds).
'b'+'ice'='BICE'

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

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