Created attachment 104368 [details]
The icon which is used as a caption for the Background color dropdown usually have an element which is supposed to indicate the current color.
Unlike in toolbar, that element has the placeholder appearance, in the default theme it is an ugly red bar.
I can confirm the red bar in galaxy, while oxygen has a red pool. Not sure what should be done with it though, as removing it completely would like remove the concept that paint is being poured out of it. I think this might be a job for the UX team to decide.
Changing the placeholder color bar would effect the toolbar if it was changed, so its not worth the effort, especially as no work is going into the galaxy theme and it is highly unused.
The source files for the Galaxy theme are missing, so it’s unmaintained.