Blue

Blue H2 is produced from fossil fuels with carbon sequestration

 
Grey

Grey H2 is produced from fossil fuels and typically uses the methane steam reforming (SMR) process

 
Black Brown

Black or brown H2 is produced from coal

 
Turquoise

Turquoise H2 is obtained by the thermal cracking (‘pyrolysis’) of methane

 
Purple, Pink, Red

Purple, Pink and Red H2 are obtained by using nuclear power.

 
White

White H2 is naturally occurring hydrogen

 
Green

Green H2 is produced by water electrolysis using renewable electricity (wind, hydro, etc)