Agree on two points then another colour (3,5)

I believe the answer is:

sea green

I'm a little stuck... Click here to teach me more about this clue!

'another colour' is the definition.
'sea green' can be an answer for 'colour' (sea green is a kind of colour). I'm unsure of the 'another' bit.

'agree on two points' is the wordplay.
'two points' can mean two substitutions for 'point'.
'on' is a charade indicator (letters next to each other).
'point' becomes 'se' (SE is an example).
'point' becomes 'n'.
'agree' after 'se' is 'seagree'.
'seagree'+'n'='SEA-GREEN'

'then' is the link.

Can you help me to learn more?

(Other definitions for sea green that I've seen before include "Robespierre's shade" , "Geese ran (anag) - colour" , "Marine colour" , "Robespierre such an incorruptible (Carlyle)" .)

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

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