Vanadium,I'm a little puzzled by this. One also gets a characteristic blue glow using glass. Why should that be?
It has to do with what excited states of the medium are. It's NOT the high speed particle that is
radiating - it is the medium. The medium is being excited by the high speed particle and de-exciting
by emitting a photon. What is special about Cherenkov radiation is that all the photons from a given
high energy particle can interfere constructively. You get the constructive interference only because
the particle is faster than the photons in the medium.
But what color the glow is is due to the electron energy levels being excited in the transparent medium.
Just as in my example with "neon tubes" - neon glows red, krypton glows green, xenon glows blue,
mercury vapor glows blue.....
Dr. Gregory Greenman