Automatically setting certain strings in colour

[Andrew Dunning]

I would like certain strings (*, †, ‡, ⹋, ℣., ℟., Ps.) to appear in colour when a score is rendered in one version of an output file I am producing, and to have a second black-and-white version that renders all these in black but in italics where possible (℣., ℟., Ps.). Is there something akin to \newunicodechar that allows one to change the formatting of particular strings, but only within Gregorio?