What mental processes allow you to perceive a lemon as yellow?

A lemon has no colour, but when one see a lemon, the brain process the information and make one to perceive that the lemon has yellow colour.

The mental process used by the brain to do this is divided into two stages, the first stage is reflection. When light is incident on the lemon, it reflects the light energy into one's eyes, where it is transformed into neural message. The eye is made up of three different cones which are sensitive to different frequencies of light. These cones process the color and the colour perceived by the observer depend on the type of sensitive opponent cells that are stimulated. A yellow color is perceived when the yellow sensitive opponent cells are stimulated.