alphadude.... yinze gettin me cornfuzed here. 1st ya said "we know its blue in water" which lead me to understand that you were referencing visible light wavelengths as detected by the human eye.... could be my bad, ya no? but then ya gets inta yer polychromatic stuff.... so now i needs to know whatinell yer knowledge base is 'n what are yer discussion boundaries?
in most media blue light predominates over longer wavelengths of light, not to say there aren't other wavelengths in the spectrum produced. but, getting back to yer original question..."what color is cherenkov in air", note that the solar tower atmospheric cherenkov effect experiment (stacee) "uses a large field of solar mirrors (heliostats) at the National Solar Thermal Test Facility near Albuequerque, NM. These mirrors were built for solar energy research conducted during the daytime. STACEE uses the mirrors at night for astronomy. The mirrors collect quick flashes of blue Cherenkov light that result from gamma-ray interactions in the atmosphere. The Cherenkov light is then detected and recorded by the STACEE equipment."