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 Dosage and Protocol: A Medical Provider's Guide to the 30 Day Cycle Perfect B Effect of high dose N acetyl cysteine on the clinical outcome of patients with diabetic peripheral neuropathy: a randomized controlled study Diabetology & Metabolic Syndrome Springer Nature Link Skin Perfection GHK Cu Copper Peptide Serum Booster, 1 Percent Blue Liquid For Face, Neck, Body, Hair, And Scalp, 0.5 oz Walmart.com