GHK Cu 50mg Copper Tripeptide Research Compound 99% What Peptides Are Legal in the U.S.? Understanding FDA Approval, Compounding, and the Legal Gray Areas Holt Law GHK Cu 50mg 100mg Copper Peptide (RUO) Tide Labs Tide Labs 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