Hi Terry

That option will not work on any white area or black, with greys it has a limited effect depending on the level of grey,

AFAICS for all other hues, the colour is shifted in the direction you drag the center of the colour wheel.

A colour shifting algorithm is, IIRC, an addition of the shift, followed by a multipication/division process to bring all the levels back into there correct relative positions while maintaining the same 'brightness' thus White cannot be shifted because it is already full Red, Green and Blue and Black cannot be shifted because it has no Reg, Green or Blue

HTH

John