GHK Cu (50mg) Your Peptide Brand 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 GHK CU for Sale Tripeptide 1 3rd Party Tested US Made What are grey market peptides?, Theyve become more common lately, especially online. These are peptides sold outside standard medical channels, often with unclear sourcing and inconsistent quality.