Dark colours bless a mix (6)

I believe the answer is:

sables

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

'dark colours' is the definition.
'sables' can be an answer for 'colours' (sable is a kind of colour). I am not sure about the 'dark' bit.

'bless a mix' is the wordplay.
'mix' indicates anagramming the letters.
'bless'+'a'='blessa'
'blessa' anagrammed gives 'SABLES'.

Can you help me to learn more?

(Another definition for sables that I've seen is " Small black animals with fine fur".)

I've seen this clue in The Mirror.

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