The human retina contain three special color cones that allow us to see color. It is a combination of these red, blue and green cones that allow us to see different colors. When we different colors, a proportion of the different colors cones are excited that allow the brain to interpret different color themes.
The human eye is a miracle and can see up to a 100 different shades. With a single cone. This means that the entire eye can see up to a million shades. Some researchers say that certain people have an extra orange cone that enables them to see up to a 100 million shades.
Most humans happen to be trichromatic. This means that they carry three different types of cones in their retina namely for the colors red, green, and blue. The information that their brain receives from these three different cones is combined so as to produce the perception of color.
Each cone allows the human eye to differentiate between 100 separate shades. Combining this exponentially, the human eye is capable of seeing 1 million shades. Some people also tend to have four cones, which includes an orange cone. This allows them to see 100 million shades. According to researchers, women are more likely to have four cones as compared to men.