I am reading Dan Broughton's answer in replying to the question "why does the gas from dry ice flow down" here.
According to the answer, the fog is water's color and water is condensed and suspended in the CO2. Do you agree with this answer? If so then should water have color? I see some documents saying that it is nearly colorless.
Why does the gas from dry ice flow down?
Dry ice is simply the common term used for solid carbon dioxide (CO2), so the gas coming off of the dry ice is CO2 gas. CO2 gas has a density of 1.96 kg/m^3 and air (78% N, 21% O2) is 1.29 kg/m^3. Since the CO2 is more dense, it sinks in air.
But CO2 is colorless, so what makes it appear as a white mist? As the gas sublimes (change directly from solid to gas), it comes off of the dry ice at -78.5 C (-109.2 F). Being well below the freezing point of water, any moisture in the air surrounding the dry ice condenses and is suspended in the CO2, creating the cloud/fog effect that we can see.
These two phenomena combined are what create the fog that flows along the ground.