I believe it’s the 'paper-item-icon’s, and theming the active colour works (as you can see in the ‘Configuration’ gear icon), but the rest of the icon colours seem hard-coded. Has anyone had any success with it? I love dark themes but the icons look really bad in them.
I’m beginning to think it’s not possible in its current state, because I’ve looked at all the other themes and none of them seem to have changed these icons.