The retina is at the posterior part of the eye. It contains cells that respond to light. It contains two types of photoreceptors, which are rods and cones. Rods are most sensitive to light; a human eye contains about 125 million rods; they are necessary for seeing in dim light.
Cones are best in bright light and are not sensitive to light. However, they are sensitive to some types of colors, which are green, red, or blue. There are between 6 to 7 million cones in the eye and are used mainly for receiving sharp, accurate images and for distinguishing colors. The brains receive signals from the cones, which then translate these messages into the perception of color; this is why colors cannot be seen well in dark places.
The answer to this is the cone cell. If you are not too familiar with this, this is a type of cell found in the eye that will usually respond to the various wavelengths of light differently. This explains why we can determine that there are different colors. This type of cell works best under bright light.
Some people have problematic cone cells that are unable to process the various wavelengths of light. This can result in color blindness. Men are more prone to this condition more than others. The different cones of the eyes are more sensitive to red, blue, and green colors as compared to the other colors that we can find.