Processes for preparing color stable red-emitting phosphors include contacting a complex fluoride phosphor of formula I with a first fluorine-containing oxidizing agent in gaseous form at a first temperature ranging from 200° C. to 700° C. to form a first product phosphor, contacting the first product phosphor in particulate form with a solution of a compound of formula II in aqueous hydrofluoric acid to form a treated phosphor, and contacting the treated phosphor with a second fluorine-containing oxidizing agent in gaseous form at a second temperature