what are the particles of light?

Answer 1

Technically they are not particles (they are packets of energy or quanta) - even though sometimes they can behave like particles and sometimes like waves.

They are called Photons. Every bit of the EM spectrum relies upon photons as the energy carrier. i.e. Radio photons, X-Ray Photons, Visible Light photons etc.

They all travel with the same speed in a vacuum which is 3 x 10^8 metres per second (or 300,000,000 metres per second).

Answer 2

photons- though calling them particles is not exactly correct. Wave nature of photons is also dominant.