GHK Cu: The Peptide That Rebuilds, Repairs & Rejuvenates Boston Health Longevity GHK Cu Youthful Skin, Healthy Cells, Vibrant You. GHK CU 100mg 99%+ Purity, COA Verified Copper Peptide Serum for Dull & Mature Skin VALNCIA 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