Applying color class None via the Stationery Pad is working for me now, in the public release v5.
EDIT: actually, no it is not! Or at least, it is working on some NEFs, but not others. I will send two NEFs to you Kirk to see what you can make of it. Setting color to None works on one, but not the other. Maybe it has something to do with whether the color class has been changed in NX2.
Thanks,
Mike