I'm facing the same problem. I have treeviews and userobjects that are displayed with different background colors depending on the displyed data coming from the database.
I have learned that it is not possible to change colors at runtime when using UI theme. Either I have to disable drawing for an object completely lacking of the advantages of theming or I have theming with only one color possible.
Is that still correct and are you planning to make changes at runtime to a specific object possible?
I think this would greatly improve theming. In my application different colors are indicating different states of data and is very useful for the users. Not everything can be displayed with datawindows.