Vision is created by utilizing two properties of light, energy(intensity) and frequency (wavelength) of stimulus.

It is the sensation that allows us to discriminate uniform surfaces of equal brightness

It is important in the perception of form where colours facilitate detecting borders of objects.

Role of photoreceptors

Cones are colour blind producing a univariant response reflecting only the amount of energy they absorb.

In order to detect objects by differences in spectral reflectance, two or more different types of cones are needed.

Two physically distinct stimuli appear as different colors only if they produce different relative activations in at least two cone types; conversely, any pair of physically distinct stimuli that activate the cone types in the same relative amount appear the same

This is why a unit area of achromatic space is smaller than a unit area of chromatic space.

Role of Horizontal cells

Role of Bipolar and Ganglion cells

L+M+ L-M-

Cone-opponent retinal ganglion cells come in four varieties: L-on/M-off, M-on/L-off, S- on/ (LM)-off, and (LM)-on/S-off

Thus, there are three channels of information from retina to cortex, which are distinct from each other not only in their chromatic properties but also in their anatomical substrate

L-M signals target the middle input layer (4Cβ), S-(L+M)(“Blue ON”) signals target the upper input layers (2/3 and 4A), and (L+M)-S (“Blue OFF”) signals are narrowly stratified in 4A

SIMPLE cells show orientation selectivity. COMPLEX cells, also show orientation selectivity but less related to the location of the stimulus. HYPERCOMPLEX cells, are orientation selective but are "end-stopped" being inhibited if the oriented stimulus is too long.

Color likely depends on both single- opponent and double opponent neurons, and on the further processing of their signals.

Single-opponent cells are ideal for signaling the color of a region covering the receptive field. Double-opponent cells are capable of signaling color contrast, color boundaries and contributing to color constancy