Choose the CORRECT word to complete the sentence.
The artist added some earthy green tones to `_________` the rich reds in his oil painting.

A Complement.

explanation

Complement can be a verb meaning to complete something or bring it to fullness. Complement can also be a noun meaning a thing that completes something or brings it to perfection. So, the correct sentence is: The artist added some earthy green tones to complement the rich reds in his oil painting.