What is a suitable way to mute an intense blue-green while retaining its colour character?

Correct answer: Add a very small amount of its red-orange complement

The governing concept is complementary neutralisation: a colour’s complement reduces its chromatic intensity. Red-orange is opposite blue-green on the colour wheel, so adding a very small amount can mute the mixture while preserving its general blue-green character. A large amount would make it dull or brownish, white would mainly create a tint, and extra blue would increase the cool bias rather than mute it.