Chrome alum (Chem.), a dark violet substance, (SO4)3Cr2.K2SO4.24H2O, analogous to, and crystallizing like, common alum. It is regarded as a double sulphate of chromium and potassium. -- Chrome green (a) The green oxide of chromium, Cr2O3, used in enamel painting, and glass staining. (b) A pigment made by mixing chrome yellow with Prussian blue. -- Chrome red, a beautiful red pigment originally prepared from the basic chromate of lead, but now made from red oxide of lead. -- Chrome yellow, a brilliant yellow pigment, PbCrO4, used by painters.