What is window background color in dark mode?

How do make a custom control blend into a dark mode window?

The default background color of a window <> FillColor in dark mode.

For most controls like listboxes, ContainerControls, you can use

g.clearRect(0, 0, g.width, g.height)

To get the control to blend into the window.

But how do I get the actual color of the window for when I’m painting the background of my own graphics objects that are not directly associated with a window? I want my background to blend into the window. Or am I going about this wrong and have to do some kind of alpha?

listbox.HasHeading is on

header HasHaeding is out is everything black
header HasHaeding is on = header black
Background lines = dark gray