What is the difference between grey, blue and green hydrogen?

Hydrogen has no color. The color of the hydrogen refers to its production process.

• ‘Grey’ refers to the origin of natural gas which is typically cracked in a steam methane reformer. During this reforming process, CO₂ is produced as a side product.
• The hydrogen becomes ‘blue’ when the CO₂ from its production process is captured and stored.
• If the hydrogen is produced by green electricity through an electrolysis process, the hydrogen is tagged as ‘green’.