Working fine over here.
Things to check out:
1. Does your modified theater mode still have some element named #InfoBar ?
If not, your soundgraph won't be positioned anywhere in sight because its location references that aforementioned element.
2. The soundgraph element accepts all of these attributes:
bdr="0,255,0" fg="0,0,230" fg2="255,255,0" bg="250,0,0"
Try inserting fg2 as it influences the color of the inner-most section - maybe that's one of the colours that you are looking to change?
3. Your bg has a transparency effect (the "10") going on there.
So maybe, the black colour is there but just faint enough for you not to see it.