Essential GHK Cu Serum: What It Is, How It Works, and Why It Matters f Bacteriostaticwater.com GHK Cu 100MG NuRev Peptides The Effect of the Human Peptide GHK on Gene Expression Relevant to Nervous System Function and Cognitive Decline 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