The human eye, and so human perception, is tuned to the range of wavelengths of light that make up the visible spectrum and so to the corresponding spectral colours between red and violet.
To be exact, spectral colour is a colour corresponding to a single wavelength of visible light, but in everyday terms, spectral colours are usually composed of a narrow band of adjacent wavelengths.
Because of the way the eye works, we can see all the colours of the visible spectrum when red, green and blue lights are combined at different intensities.
The RGB colour model is designed to provide the exact stimuli to the light-sensitive cone cells in the retina to illicit perception of any predetermined colour.
Mixing wavelengths of light corresponding with the RGB primaries enables the human eye to see almost any imaginable colour including colours such as magenta that are not part of the visible spectrum.
Rod and cone cells are the photoreceptor cells in the human retina that respond to light.
Ganglion cells are the retinal neurons that receive and integrate visual information from photoreceptor cells and then transmit it to the brain via the optic nerve.
The complex network of interneurons in the human eye plays an important role in the processing and integration of visual information before transmitting it to the brain.
This network is also responsible for various visual functions, including spatial filtering, contrast enhancement, and colour opponent processing.