The article discusses the importance of understanding the fuel used in hydrogen fuel cells and hydrogen internal combustion engines (H2-ICE) and its impact on performance and environmental sustainability. Various terms and color codes like green, blue, grey, and pink are used to categorize hydrogen based on production methods. Hydrogen is abundant but must be extracted from sources like water, methane, and oil, leading to different production methods and energy requirements. The cleaner the source of energy used, the better the carbon profile of the hydrogen produced. The article highlights the role of color codes and carbon intensity scores in helping industries and governments set standards for this emerging fuel that can reduce emissions in medium and heavy-duty trucking. The importance of recognizing impurities in hydrogen, especially for fuel cells, is emphasized to ensure optimal performance. Different categories of hydrogen like green, yellow, grey, blue, turquoise, and pink are explained based on their production methods and environmental impact. While color codes help differentiate hydrogen sourcing, carbon intensity values provide a more accurate evaluation of its carbon footprint. The Department of Energy in the USA focuses on carbon intensity values in its National Clean Hydrogen Strategy and Roadmap, disregarding the color-coded classifications. Overall, the article presents a positive outlook on hydrogen, emphasizing the importance of sustainable production methods and environmental considerations in the transition to hydrogen fuel.