CSS for closed parent node bullet points?

I would like to experiment with user styles that have different colors for regular bullet points and those that have a ring around them (closed parent nodes). But I can’t find the rule in the CSS in order to test it out. So I don’t even know if it is possible. Anyone know the rule I would use in my custom user stylesheet?

.Node-self.is-collapsed > .Node-bullet:before

Thanks Piotr! Worked like a charm!