Working with the new release of Dorico I find that if voice colours are enabled, notehead transparency settings are ignored and notes you have hidden by setting the alpha channel value to 0 are displayed willy-nilly. Not sure if this is new with this release, but I haven’t noticed it before and it doesn’t seem desirable.
Voice colours and the color property are two absolutely different things you should not melt. Voice colours are a visual help to emphasize the fact that different notes are on different voices, but this would never be printed. Colour property, on the other hand, is an editorial choice.