A coating material includes silicon and/or aluminum, hydrogen and any two or more of oxygen, nitrogen, carbon, and fluorine. The coating material exhibits a hardness of about 17 GPa or greater and an optical band gap of about 3.5 eV or greater. The coating material includes, in atomic %, silicon and/or aluminum in an amount of about 40 or greater, hydrogen in an amount in the range from about 1 to about 25, nitrogen in an amount of about 30 or greater, oxygen in an amount in the range from about 0 to about 7.5, carbon in an amount in the range from about 0 to about 10, and optionally, fluorine and/or boron. Articles including the coating material may exhibit an average transmittance of about 85% or greater over an optical wavelength regime in the range from about 380 nm to about 720 nm and colorlessness.