A GHK Cu face serum appears blue because the active ingredient, GHK Cu (copper peptide), is naturally a blue colored powder, meaning its inherent color transfers to the serum when mixed in; this blue hue Skincare Copper Peptide GHk Cu & Methylene Blue Global Ubuy 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 Glutathione Injections: Side Effects & Benefits Glutathione Injection: Cost, Benefits & Side Effects