I tried to modify properties of JvTabBar, but it does not work. I assigned JvTabBarXPPainter to JvTabBar, but it only changed "FixedTabSize" properties. All the other cannot be changed. What interests me is to change the background color and font.
You can use TJvModernTabBarPainter and assign it to the JvTabBar. It allows you to modify all properties. The XP-Painter paints with the theming API and you can't change its colors unless you change the XP theming style system wide.