What are Oil Paints and Pigments?

Light/color:

Light is a collection of energy-particles (photons) that travel in waves.

Sensors in the human eye can detect some wavelengths, and the human brain translates different wavelengths as different colors.

When light that consists of all the detectable wavelengths reach the eye, like from looking at the sun or a lamp, the human brain will translate it as white or yellowish white.

Therefore, colors are a characteristic of the human sight, meaning the translation of different wavelengths to different colors.

Pigment:

A pigment is a substance or material that absorbs a portion of the visible wavelengths (light), and reflects the rest.

Chlorophyll, for example, is a pigment that exists in plants, and is essential for photosynthesis.

The Chlorophyll pigment absorbs many wavelengths, but reflects the wavelengths we translate as green. That is the reason we see plants as if they are green.

In other words, a pigment is a substance that changes the color of light by selective absorption of wavelengths.

Oil paints:

Oil paints are pigments (dry powder), mixed with a binder, usually linseed oil.

Oil based paints do NOT dry; they become solid. When linseed oil meets oxygen from the air, the process of oxidation begins (absorption of oxygen atoms), and polymerization (oil molecules react to form polymers, which are huge molecules).