The human brain understands color in a very interesting manner.  Color is technically defined as the visual effect that is caused by the spectral composition of the light emitted, transmitted, or reflected by objects. Light and reflection greatly affect vision and perception of color. Read more on How We See Color...

The human brain understands color in a very interesting manner.  Color is technically defined as the visual effect that is caused by the spectral composition of the light emitted, transmitted, or reflected by objects. Light and reflection greatly affect vision and perception of color. 

What the eye actually interprets as color is known as its color effect.  When an object is hit or bombarded with light rays, the object absorbs certain waves and reflects others.  The absorption or reflection of light rays determines the color effect.  For example, when you see a blue ball what is actually observed is the reflection of only blue light and the absorption all other light. Daylight is white light and it is made up of numerous waves or impulses each having different dimensions or wavelengths.  When separated, any single wavelength will produce a specific color impression to the human eye. So in the case of the blue ball, the ball does not have color itself, the light generates the color.  In conclusion, color is the reflection of specific wavelengths of light rays off of an object.

The functions of the various components of the human eye that participate in the vision process are known. Light that reflects off of objects around us is imaged onto the retina by the lens. The retina, consisting of three layers of neurons (photoreceptor, bipolar and ganglion) is responsible for detecting the light from these images and then causing impulses to be sent to the brain along the optic nerve. The brain decodes these images into information that we know as vision.

There are two kinds of photoreceptor cells in the retina, there are rod cells and cone cells.  The rod cells are responsive to low light and the cone cells are responsive to color in bright conditions and are used for fine detail.  The difference between these types of cells explains why color is not seen in low light. Rods and cones form an uneven mosaic within the retina, with rods generally outnumbering cones more than 10 to 1—except in the retina's center, or fovea.

The difference between black and white also helps to understand how the perception of color works. The color white occurs when all light waves are reflected from a surface, the reflection will make the surface appear to be white. The color black occurs when all light waves are absorbed by a surface. Thus, in the case of black color the energy of light waves is converted into heat when absorbed. Additionally, wearing white or light colored clothing during hot summer days takes advantage of the reflection quality of white.

The colored light in the visible spectrum ranges from red to violet. We can see this process by passing sunlight (white light) through a prism. Upon entering the prism, white light refracts (is bent, causing light waves of different lengths to be revealed, red having the longest wave length and violet having the shortest) into the visible spectrum.

These basic principles are the foundation to understanding how we see color.