Analog of %`bc for %tt ?

Is there analog of %`bc which works only for %bt but the one which works on %tt ?

There is currently no equivalent for %tt. The background coloure can be set initially using %`bg. The only way to set the colour dynamically is to call set_control_back_colour@(hwnd, RGB@(r,g,b)) where hwnd is the integer(7) value obtained via %lc.