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 89030 95 5 GHK Cu Gly His Lys Cu Copper Tripeptide 1; Prezatide copper GHK Cu 100mg Peak Haven Theoretical study of copper binding to GHK peptide ScienceDirect Intermediate Cu(II) Thiolate Species in the Reduction of Cu(II)GHK by Glutathione: A Handy Chelate for Biological Cu(II) Reduction Inorganic Chemistry