for example glazes of violet or green on métal, on a face in the shadows, in the shadows of clothes; I dilute with W Spirit, ad when the flat is dry, give a rapid glaze in the shadow with highly diluted colour, wait one day and repeat until subtle tone appear, ....
I did for Elerinaa Elven bust with the skin, against the Mars black of the bust clothing to give a litte bit of warm; you can give a glaze green or blue to the second to cool the color slightly and enforce the contrast betwwen warm and cool....