Messing around with union blue to find a colour scheme that will fit a dark panel. Until the panel buttons become themeable that orange close button looks horrible on top of any colour except dark, light or grey panels.
Cheers! Minimise and unmaximise both follow the text colour in the panel ("electric" blue). I'll see if I can post a second preview image that shows this. The maximised close button seems hard coded and wont react to changes in the theme. Maybe I just haven't found the right gtk command yet.