From what I understand so far about Blender, wherever the mouse cursor is hovering over, it becomes the active region.
Currently, Blender slightly changes the tint of a menu's header as you hover your cursor on and off from the menu. But that small change is barely noticeable.
Is there a blender UI addon that can let the user create a custom color for both the active and non-active Headers or active/non-active Window Backgrounds?
It helps to know what is active, especially on large high resolution monitors.