A treatment method for modifying the reflected color of a sapphire material surface comprising bombardment by a single- and/or multi-charged gas ion beam so as to modify the reflected color of the treated sapphire material surface, wherein the ions are selected from ions of the elements from the list consisting of helium (He), neon (Ne), argon (Ar), krypton (Kr), xenon (Xe), boron (B), carbon (C), nitrogen (N), oxygen (O), fluorine (F), silicon (Si), phosphorus (P) and sulphur (S).