What Causes the Color of Hydrogen Gas?

[papernuke]

Hydrogen gas is supposed to be colorless, but what causes the murky grey-white color of the hydrogen gas produced in this reaction?

http://www.youtube.com/watch?v=oQz5YEsx7Fo&feature=related

skip to 00:30

 

[Nessdude14]

My guess would be that it's water vapor created from the heat of the reaction.

 

[papernuke]

My guess would be that it's water vapor created from the heat of the reaction.

Oh yeah, makes sense.
Thanks!