Button Background Color

I don’t think there’s a way to do that.
I’d go for changing the text so that you get additional information that way, maybe usieng an emoji with a colourted background if that would help. See this threadd for more info:

Or, you could go for adding an LED that you can change the colour of at any time, or labelled value widget next to the switch where you can change the text and the text colour.

Pete.