Blue star kachina and comet ISON explained using Cherenkov radiation

Why does comet ISON have a blue coma and at the same time have a reddish tail?

The answer is, ISON is really a red comet, but is also emitting Cherenkov radiation (blue light) at the same time.

The Cherenkov radiation is produced by neutron-antineutron oscillations taking place at ISON. When a neutron oscillates into an antineutron in the nucleus, it quickly annihilates and produces multiple pions which emit Cherenkov radiation.
[link to www.int.washington.edu]

Cherenkov radiation is electromagnetic radiation emitted when a charged particle (such as an electron) passes through a dielectric medium at a speed greater than the phase velocity of light in that medium.

The frequency spectrum of Cherenkov radiation by a particle is given by the Frank–Tamm formula. Unlike fluorescence or emission spectra that have characteristic spectral peaks, Cherenkov radiation is continuous. Around the visible spectrum, the relative intensity per unit frequency is approximately proportional to the frequency. That is, higher frequencies (shorter wavelengths) are more intense in Cherenkov radiation. This is why visible Cherenkov radiation is observed to be brilliant blue. In fact, most Cherenkov radiation is in the ultraviolet spectrum—it is only with sufficiently accelerated charges that it even becomes visible; the sensitivity of the human eye peaks at green, and is very low in the violet portion of the spectrum.
[link to en.wikipedia.org]