How do we Change Colours?

Color from Light

The color of anything depends on the type of light sent to our eyes; light is necessary if we are to have any perception of color at all. An object is "colored," as stated above, because of the light it reflects—all other colors are absorbed into that specific object. So then, an apple appears red because it reflects red light. 

White light from the sun contains all the possible color variations. Yet, the human eye can only respond to certain colors and wavelengths, and not everyone sees the same colors or exact same shades of a color. We are capable of seeing color because our eyes have light and color-sensitive receptors.

These receptors are called rods (receptive to amounts of light) and cones (sensitive to colors). Being able to see color is a sensation, just like smelling a pie fresh out of the oven or tasting your favorite meal. Different foods smell and taste different to each person, and likewise, no color is seen exactly the same by two people, because each person's rods and cones vary.   

Color
The primary colors of light are red, blue, and green, and the secondary are yellow, cyan, and magenta. It is very important to know that mixing pigment and mixing light are very different. Red and green paint, for example, make brown paint, but red and green light make yellow light. When beams of light are mixed without any absorption, an additive process occurs. The more we mix the beams, the closer they get to being white light. However, when we put light through a color filter, a subtractive process occurs. Some wavelengths of light are being absorbed (subtracted) and we only see the wavelengths that are selectively given off.