Hmm, it doesn't seem possible to add more than 1 layer to the playlist.
i.e.
borderbr overlayer
borderbr underlayer
What I wanted to do was to use the underlayer (the background) being able to change it's colour with the RGB sliders so there would be 3 of them plus a white underbackground under those 3 and have a detail layer on top showing highlights etc..
and be able to use those for the playlist (well main SUI) and resize it.