Color-coded nomenclature of colorless hydrogen: which one is better?

Abstract

This highlight provides an accessible overview of hydrogen production technologies, structured around a widely adopted color coded typology: grey, blue, green, yellow, pink, turquoise, and white, based on their technoeconomic and environmental characteristics. Leveraging a substantial literature base, it offers an entry level synthesis of key indicators, including the Levelized Cost of Hydrogen, Levelized Cost of Energy, and Life Cycle Assessment, to compare production pathways. Grey and blue hydrogen remain the most cost effective options at present, but raise environmental concerns. Green hydrogen, derived from renewable powered electrolysis, offers the lowest emissions but faces high cost and infrastructure hurdles. Emerging forms, including pink, turquoise, and white hydrogen, introduce novel opportunities and challenges, from nuclear integration to natural hydrogen extraction. The paper also outlines current policy drivers, emphasizing that international cooperation, regulatory alignment, and innovation are essential to realizing hydrogen's role in the global energy transition. This review is intended as a starting point for researchers, policymakers, and practitioners seeking a clear introduction to the hydrogen landscape.