White light, or most kinds of light that we use for illumination including our sun, contains all the colors in the visible spectrum, in varying degrees of proportions depending on the light source. For example, a typical incandescent household light bulb gives off more red light than a common office fluorescent light, which usually produces more bluish light. A full-spectrum light simulates the full range of light found in sunlight.

Even sunlight falling on objects at different times of day can make them appear to have color shifts. The same object can appear differently in morning sun than at noon, and different still at sunset. However, the human eye and brain tend to compensate for this color shift, interpreting colors of objects consistently in varying lightings. The camera shows the difference.

When white light is passed through an object that bends or refracts it, the individual spectral hues in the light spread and separate at individual angles as they emerge from the refracting object. The historic scientist Isaac Newton was aware in the late 1600's that if white light was passed through a glass prism, distinct bands of separated colors could be observed, when projected onto a white surface.

Newton discovered that if the separated spectrum of colors was then passed through a second prism, the refracted hues could be recombined to emerge as white light once again. His findings disproved the prevailing belief of his time that the prism added the colors, sparking much debate about the nature of light and color.

The prism effect can be seen when we look at a rainbow, which contains the spectral hues refracted through water droplets in the atmosphere. Two people standing next to one another will likely see the refraction from different droplets of water, creating a separate rainbow for each of them. Since the violet wavelengths are shorter, a primary rainbow will always have violet on the inside (inner arc) and red on the outside. Dimmer secondary rainbows caused by another refraction inside the water droplets may also be visible, appearing with their colors reversed.

When white light strikes a colored surface, the surface absorbs all the spectral hues except those that are contained in the pigment or surface color of the object, which are reflected. For example, when light falls on a red tomato, its surface will absorb all colors except the red, which is reflected back. This is why the tomato appears red to a human eye. If the light falls on a blue table, the surface absorbs all colors except blue, which is reflected back for us to see.

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