Question

Question #0b943

Answer 1

Electrons have no colour.

What is you see is the effect that electrons have on the coating of the cathode ray tube (CRT), in your case (probably) zinc sulphide `ZnS`.

The electrons that hit the zinc sulphide bring it into a higher energetic state, and when it falls back, it emits light, in this case green.

If you use other so-called phosphors in stead of `ZnS`, you get differently coloured light.

Something similar happens in luminescent tubes, where the invisible UV light is 'translated' into different colours of visible light to give an altogether white-light effect.