Colour is light of a specific wavelength or a mixture of proportions of two or more specific wavelengths of light. These wavelengths are typically regarded as those within the visible range of the spectrum while there are some colours (wavelengths of light) that are visible only to certain species.
The rainbow sorts out many of the visible wavelengths of light by the degree of their respective angles of refraction within a raindrop. Shorter (bluer) wavelengths are refracted (bend) more and so appear in a different band in the rainbow than their longer (redder) counterparts.
These different wavelengths of light (colours) are given names according to things that are widely associated with their appearence; (green grass, red rose, blue sky, orange orange), or colours may be assigned to standard wavelengths.
Colour perception begins in the eye where colour receptors have greater sensitivity to a specific range of wavelengths of light which are then processed interpreted and cataloged by the brain.
The point of all this is that we all perceive the same colours, the difference is in how these colours are sensed, processed and interpreted by a particular individual. Fortunately there is a significant ability to agree on the identification of various colours that makes them a valuable tool for communicating this aspect of what we see.