Cats, dogs, and many nocturnal creatures appear to have glowing eyes because the back of their eyeballs include a special reflective layer called the tapetum lucidum.
This helps animals (cats in this case) see better in low light by working like a mirror on the retina to reflect the light back through the eyes, giving them a second chance to absorb the light.
The colors seem more visible at night because the pupils are dilated wider than during the day, allowing more of the tapetum lucidum to be visible.