Aloha..
The BG of I\O and Routing Matrix is (Window background)
The text BG 'menu' is (Windows edit background)
The I\O text is (I\O Windows text)
The text in the routing matrix is (Windows text)
Plugin pin is also (Window background) and the text (Window text)
The envelope is, well, you guessed it.
The parameter BG & text is what you set in Windows OS, just like the reaplugs.
I sure would like to have more detailed individual control of everything but, there you go, until my brain gets an update, or Reaper.