1% GHK CU solution: is this applied directly on skin or diluted further? : r DIYaesthetics Best Time to Take Glutathione: Morning or Night? Healeo Nutrition GHK Cu Copper Peptide Serum 1% Black Tie Health 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