Code review comment for lp://staging/~gcollura/content-hub/fix-1384490

I think it's best if we pick up the colour from the Theme palette as this is how the developer should be customising colour throughout the app, however I think we need to do some extra things to match the way the UITK uses these properties, I'll have a bit of look into this and get back to you on what I find.

Aside from that it looks like you've got a couple of typos for Qt.rgba listed as Qt.rbga (g and b switched around), so dark layouts still get the white background. However, with these corrected the apps box for light backgrounds becomes gray, so we might need to think about that a bit more.