Oxide of Chromium (PG17)
I went to town on this one and added five extra mixes. Interestingly, I avoided it for years thinking it was dull but was intrigued that it was regularly used by Shirley Trevena whose work is far from dull. Once I tried it, I understood and have since used it in both my UK and Caribbean scenes.
If I were to describe the way this pigment interacts with the others, I'd say it has good manners, unlike say phthalo blue or magenta which have to hog the conversation and be the centre of attraction - I still love them though!