Light can be defined in many ways.
A photon, a wave form, a particle, an electromagnetic frequency. Light behaves as both a physical particle and a wave.
What we think of as light is a small part of the electromagnetic spectrum known as human visible light, which the cells in human eyes are sensitive to. Most animals eyes are sensitive to a similar range.
Insects, birds, and even cats & dogs can see some degree of UV light, while some other animals can see infrared; fish, snakes, and even mosquitoes!
The mammalian brain interprets/decodes light into ‘colour’. The wavelength or frequency of the light is what determines our perceived colour. A longer wavelength looks like red while a shorter wavelength appears to be blue.
So colour is not intrinsic to the universe, but a creation of our minds. Only representing a tiny fraction of the full electromagnetic spectrum. Just a photon at a certain frequency.
The basic form of light is a stream of photons, oscillating at a specific wavelength.