Concur with former nurse about main colour? (3-5)

I believe the answer is:

sea-green

'main colour?' is the definition.
(the main is an old name for the sea)

'concur with former nurse about' is the wordplay.
'concur with' becomes 'agree'.
'former nurse' becomes 'sen' (I've seen this in other clues).
'about' means one lot of letters goes inside another.
'agree' going into 'sen' is 'SEA-GREEN'.

(Another definition for sea-green that I've seen is " Robespierre's shade".)

I've seen this clue in The Times.

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