Cherenkov Radiation is caused when a charged particle moves faster than light would in a medium. And because of the properties of this radiation, the photons that you see are of higher frequencies (shorter wavelengths). The shorter the wavelength, the more blue the light appears. This is why nuclear reactors glow.
What color is the glow of radium?
Radon ordinarily exists as a gas, but as it is cooled it becomes phosphorescent yellow, deepening to glowing red as it is chilled below its freezing point. Actinium also glows. Actinium is a radioactive metal that emits a pale blue light in a darkened room. Nuclear reactions may produce a glow.
Is plutonium really green?
Plutonium is a radioactive chemical element with symbol Pu and atomic number 94. It is an actinide metal of silvery-gray appearance that tarnishes when exposed to air, and forms a dull coating when oxidized.