The copper(II) binding tripeptide GHK, a valuable crystallization and phasing tag for macromolecular crystallography Buy GHK Cu Exceptional 99%+ Purity Third Party COA Included Your copper peptide product should be this exact blue. If it isn't, you already have your answer. GHK Cu is blue because of coordination chemistry, not dye. The Cu ion at the center GHK Cu GHK Cu: The Elegant Copper Peptide for Skin and Scalp Renewal Renew Vitality