Hi,

I am running Arch linux with plasma workspace 5.5.3-2. Some, but not all, systray icons do not have a transparent border, but a black one. Currently, this happens for Skype and Zim, but the "stock" tray icons and the one for KeePassX look just fine.
I am using the same applications on my laptop, using the same plasma version. The only potentially relevant difference I can think of is that on my laptop, I am using an Intel graphics card, whereas my desktop pc is equipped with a Radeon HD7850, running the opensource radeon driver.

Do you have an idea how I could fix this?

https://bugs.kde.org/show_bug.cgi?id=356937

Huh, interesting, thanks for the link.
It's weird, though, that it's working fine on my laptop and just randomly breaking on my desktop. I guess I'll wait for a patch then.