Which one of the following is the colour of hydrogen gas?

Hydrogen gas (H2) is a diatomic molecule that is naturally colourless, odourless, and tasteless [1]. At standard temperature and pressure, it exists as an invisible gas [1]. While the energy industry uses a 'colour spectrum' (such as green, blue, or grey hydrogen) to categorize the gas based on its production method and carbon intensity, these are merely nicknames or codes; the physical gas itself remains entirely colourless regardless of its classification. Hydrogen is the lightest and most abundant element in the universe, consisting of one proton and one electron [1]. When it burns in air, it produces a pale blue flame that is almost invisible to the naked eye. It is highly flammable and can form explosive mixtures, but it does not possess any inherent visual pigmentation like yellow, orange, or black [1].

Sources

1. [1] https://pubchem.ncbi.nlm.nih.gov/compound/Hydrogen