See bug 151900 for context, that bug has to be solved first.
Once that's done, the UI should be improved (the Theme tab page):
Looking at the competition (PowerPoint), what they have is you go to slide master view, and then the Slide Master tab on the ribbon has a colors dropdown. Each item in that dropdown provides a set of colors. Only an additional button below the dropdown opens an inner dialog to edit individual colors.
The idea (from Heiko, but I agree) is that most users don't want to specify individual colors, rather they just want to pick one set of colors from a list.
The above referred bugreport has additional columns with RGB values, those should be used for the implementation.
The task is to add such a theme color dropdown to the Theme tab page, and move most of the widgets of the original tab page into an inner dialog, available from a new button below the dropdown. (Or something equivalent, Heiko may have better ideas for the exact layout.)
As a follow-up, this may obsolete palettes of colors (which are just RGB values without names), but good to work incrementally.
Adding people to CC. I'm filing this as a bug as I don't have time to do this myself right now and it's possible Tomaz would have a student to work on this.
(In reply to Miklos Vajna from comment #0)
> The idea (from Heiko, but I agree) is that most users don't want to specify
> individual colors, rather they just want to pick one set of colors from a
See bug 151507
Tomaz fixed this / implemented the feature for Writer. Calc and Impress still needs doing.