Essentially a duplicate of several other tray icon issues, but leaving open for coverage of the various cases.
Hope so cause it's a bit nonsense to find the Steam icon on the tray if the user set a light desktop theme. And the icon has a greyish colour which is very popular, it really fits but also hides it.
I'm betting there's some special icon format that's just an alpha channel so the desktop environment can set the actual color itself, and Valve is using the obsolete full-color one. This has been an issue for me in KDE since always, but I had no idea Ubuntu had a built-in light theme too. This really does need to be dealt with.
Nothing extracted yet.
Since Steam has been changed to this monochrome theme there is only a light coloured variant which is cool but looks weird (like a black sheep) on the default Radiance theme. I don't know how it looks like on other distros but I guess most distros has a lighter and a darker default theme so others may also prefer a reverted/dark one tray icon. Please add it.