What is hapoening when we perceive an object to be the color orange

Let's say you've got a nice ripe orange in your hand. You walk outside, and the sunlight beams down on the orange from above. The sunlight is white light, so it contains all the different frequencies in the visible light spectrum. Many different waves of light beam down on the orange, each wave a different frequency. When a light wave strikes any object, it can do one of three things: it can be transmitted, it can be absorbed, or it can be reflected. We know that none of the light waves are transmitted through the orange. If they were, then the orange would appear transparent. Since we can't see through oranges, that means they are opaque, and that means all the light must be reflected or absorbed.

Absorption of a light wave occurs through resonance. When the frequency of a light wave matches the resonant frequency of an object, then the object vibrates at that frequency. The energy of the light wave stays in that object as thermal or vibrational energy. In other words, you never see that light wave again! Let's take this one little light wave here, which happens to be the frequency of the color violet. When this violet light wave strikes the orange, there are some molecules in the orange which resonate at that frequency. The violet light wave is absorbed by those molecules, so we never see the violet reflecting off the orange's surface. What about green? When a green light wave strikes the orange, it also resonates with some of the molecules in the skin. It gets absorbed, and so we don't see green, either. In fact, most of the frequencies inside the white sunbeam are absorbed by the orange. The only frequency that ISN'T absorbed is that of the color orange!