I made this scheme by slightly modifying DarkRedDark (under the terms of the GPL). I merely set the green and blue values of the View Background and Window Background colours to zero, so that they also become a shade of red.
I use this scheme for my root GUI windows (like when I edit system files using KWrite) as a warning to me that I can potentially damage my system from those windows.
To set this scheme for your root GUI, do kdesudo systemsettings and through that, select this like any other colour scheme.
Obviously this scheme will not be a very good visual warning if you have set DarkRedDark or some similar red/black theme for your normal user profile. I use ColorCombo114 (green/white) for that! :)