You could Edit Fixtures to make the default CMY values all 100%. This would bring up black by default. Could take a while depending on the number of fixtures you have. Another option would be to create a black palette and select that before you take the fixture to Full. Both options seem a bit counter intuitive with Full up essentially being off. I'd suggest selecting a color before going Full if avoiding the white light is your intention.
That's certainly a quick way to do it if you're changing all fixtures of a type, but it if it's a non-contiguous subset of fixtures it could take longer. :)>-
