That looks amazing!
Please tell me you did that through #base includes for the clientscheme (that should be possible if you haven't set that up already, changes like that should persist after HUD updates and don't require touching the defining color scheme files).
Define color names in Color {} section, and #base include to set a 'MenuBackgroundColor' in the BaseSettings to be 'Green' or whatever colorname was defined in the Color {} section in clientscheme should work.