Hydrogen colours are shorthand labels for how hydrogen is made. The gas itself is colourless and identical whatever its source; the colour describes the production route and, loosely, its emissions.
The main colours
| Colour | How it is made | Emissions |
|---|---|---|
| Grey | Natural gas split by steam methane reforming, CO2 released | High; most hydrogen made today |
| Blue | As grey, with most of the CO2 captured and stored | Lower; depends on capture rate and methane leaks |
| Green | Water split in an electrolyser using renewable electricity | Very low at the point of production |
| Pink | Electrolysis powered by nuclear electricity | Very low |
| Turquoise | Methane split by pyrolysis into hydrogen and solid carbon | Depends on the energy used and methane leaks |
| Brown or black | Made from coal by gasification | Highest |
Other labels, such as white for naturally occurring hydrogen, are used less consistently.
Why UK policy does not use colours
Colours ignore what matters most for the climate: the actual greenhouse gas emissions per unit of hydrogen. Blue hydrogen with poor capture can emit more than the label suggests, and electrolysis powered by a fossil-heavy grid is not clean. The UK therefore uses the Low Carbon Hydrogen Standard. To count as low carbon, hydrogen must have emissions of 20 grams of CO2 equivalent per megajoule (lower heating value) or less, calculated across production and supply. Version 4 of the standard was published in January 2026, and producers seeking government revenue support under the Hydrogen Production Revenue Support Regulations 2023 use it to show eligibility.
The first Hydrogen Allocation Round, announced in December 2023, selected 11 electrolytic (green) projects with a combined 125 MW of production capacity across England, Scotland and Wales.
Read more: Green hydrogen: how it is made and what the UK plans to use it for.