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 N2 (N Glycyl L histidyl) L lysinato(2 )]copper 89030 95 5 wiki Interplay of the CuCu distance and coordination geometry as a factor affecting the quantum efficiency in dimeric copper(i) halide complexes with derivatives of 4 pyrazolylpyrimidine 2 thiol Dalton Transactions (RSC Publishing) GHK CU (50mg) Nordsci