I was browsing Ubuntu Icon theme on internet, then I found Papirus Icon theme. From the screenshot, I can tell this icon look promising enough. So I decided to install it.
Indeed, the icon offered colorful, nice modern looking and elegant design. I think I've found a icon theme that I really like :)
Still, there are things that bother me much. It was some system icon that has the same color as the menu background color, and is therefore invisible.
User icon : If you hover the mouse to "Guest Session", the icon will be appear.
Volume icon : Same goes for volume icon
Battery icon : Invisible battery icon
My question is: How do I change these icon's color to different color (black in this case) ?
UPDATE Firefox screenshot: