Up to the seventeenth century, most theories attributed color to some sort of modification of light that was thought to occur when light interacted with matter. Light, in its purest form (such as sunlight) was thought to be colorless. However, progress in understanding color was made by Isaac Newton when in 1666 he was able to show that normal white light already contained all the colors of the spectrum, which could be separated using a prism. He also concluded from his experiments that objects have color because they selectively reflect certain colors of the spectrum while absorbing light of other colors.
Light is the small part of the electromagnetic spectrum that can affect the human sense of sight. The visible part of the spectrum (for us) ranges from 400 nm (blue) to 700 nm (red). Each wavelength value within the visible band corresponds to a distinct colour.
The visible portion of the spectrum
Parameters of light that are of interest to us:
Three attributes are used to specify a color: hue, saturation and brightness. These describe only the perception of light, not its physical properties.
Examples of (a)different hues, (b)different saturation, and (c)different brightness