Or check "Game Develop". The primary interface is a kind of weird rip-off of the MS Office ribbon, but I assume this is a custom widget. There's also a tab interface though, and this doesn't work on either the Windows or GTK versions: it's weird and has a gradient background.
In general, small details like the padding, coloration, and borders drawn around widgets seem to be slightly off on most platforms with just about very wx based GUI I've seen.
The rest of the controls (ribbon, tabs) are indeed non-native and there are no native equivalents for them, so there is not much to say here.
Generally speaking, there shouldn't be any problem with the colours unless you change them explicitly, which is a bad idea for the native controls. Not sure what is wrong with the padding and borders.