Cu Peptide Before and After: What to Expect for Skin and Hair 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 Amazon.com: GHK Cu Copper Peptide Powder 99.7%+ Pure Cosmetic Grade Ingredient for DIY Serums, Creams & Scalp Tonics Supports Collagen & Fuller Hair (1g) : Beauty & Personal Care GHK CU: How to Mix It The Peptide Report