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 Site Specific Detection of CopperPeptide Coordination in Solution Phase by Two Dimensional Infrared Spectroscopy The Journal of Physical Chemistry Letters Theoretical study of copper binding to GHK peptide ScienceDirect GHK Cu 100mg Research Compound Australia