The hydrogen colour spectrum - based on its production methods

Although hydrogen gas is colourless, it has been labeled under different colours based on the method and the energy source used for its production.

• Green hydrogen - Hydrogen produced from the splitting of water using renewable sources of energy.
• Blue hydrogen - Hydrogen produced by reforming methane or natural gas accompanied by carbon capture usage and storage (CCUS) technologies. Steam reforming of methane or natural gas leads to the emission of carbon dioxide and carbon monoxide gases which when released into the environment can lead to serious climate consequences.
• Grey Hydrogen - Hydrogen produced by steam reforming of methane or natural gas without CCUS.
• Yellow hydrogen - Hydrogen produced through electrolysis (splitting of water) by using the mixed electricity from the grid i.e., the electricity being used can come from the burning of fossil fuels.
• Purple / Pink hydrogen - Hydrogen produced through electrolysis of water using nuclear power as the electricity source.
• Turquoise hydrogen - Hydrogen produced through pyrolysing or plasmalysing methane, or natural gas. Pyrolysing methane or natural gas will yield hydrogen and solid carbon.
• Brown / Black hydrogen - Hydrogen produced through the gasification of lignite or black coal.
• White hydrogen - Naturally occurring hydrogen found in underground deposits.