I never liked phtalo green, mainly due to my ignorance on how to use it. The color always felt too vibrant and unatural to my taste. Remember me the felt pen kids use. But today, I discovered mixed with Venise Red and Burnt Sienna, you can get very interesting greys, At some point I really needed a dark value, the only way to get it (without adding an intrusive hue) was to mix ultramarine and phtalo green. For the very first time, I did a value thumbnail sketch before painting. I have to admit, it was a true help.