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 Copper Peptides GHK Cu Beef Tallow for Skin: Blue Balm with Methylene Blue, Manuka Honey & Vitamin E Natural Face and Body Moisturizer for Mature, Dry & Sensitive Skin 2oz GHK Cu Peptide Before and After Results Differentiating Changes in Glutathione Levels from Cytotoxic Events Using Multiplexed Assays