Horrrible Gas is a lethal killing thing that kills you on contact. In Little Big Planet 1, you can only pick 6 colors for the gas to be in the moon.
In Little Big Planet 2, you can pick any color of the rainbow.
How to Make Gas Really Colorful in Little Big Planet 2
Go to My Moon, open your popit, get any material and place it. Now go to the tools bag, select the gas, and tweak it to any color and 10% brightness.(It looks like that in The Factory of a Better Tomorrow.)