If it doesn't have a setting for tha inside the application, it can't be done. Did you check all?
But I'm afraid that if you need an email program with a different background color, you need a different email program. Why do you need it, by the way?
I'm working on windows mobile 6.5.3.
I created a theme, that sets the background color throughout the system.
What I need now is, to change the color of the background of the screen for a specific application (right now it's outlook, maybe there will be more).
Just to be precise: I don't want to change the theme for the whole system, but only to be able to set a different color for the outlook application.
How can this be done?