I cannot seem to set the background color for the spinner control to anything other than white. Am I being silly?
No I don’t think you are. If you set it from the property editor it will display as expected but when you run the display the background changes back to white.
If you change it manually in script it will stay as changed, so a work around would be to change the background color in the internalFrameActivated event of the Window. Not great if you have several of these throughout the project I know, but it should work.
You may want to contact support and report it as a bug.