Struggling with notification icons

[PhilW]

Hi all. I'm developing on sdk22 so I know for a fact everything will work I older hardware. However I cannot get my notification bar icon acting like other icons on my nougat phone. My current phone will invert pretty much all icons if the background is light and leave original if dark. I have also noticed on the lock screen apps using colour such as Twitter and Skype. I'm at a loss at the moment as just use a transparent png but it stays white on every background.

Thank you for your help