Color

When atoms or compounds absorb light of the proper frequency, their electrons are excited to higher energy levels. Colored compounds absorb visible (colored) light and this absorption is responsible for their color.

Our eyes perceive a mixture of all of the colors, as in the proportions in sunlight, as white light. The following figure shows how the mixture of colors that the eye perceives as white light is separated as the light passes through a prism.

As shown in the next figure, an object is seen as black if it absorbs all colors of white light. A white object reflects all colors of white light equally.

If an object absorbs all colors but one, we see the color it does not absorb. The yellow strip in the following figure absorbs red, orange, green, blue, indigo and violet light. It reflects yellow light and we see it as yellow.

The eye also uses complementary colors in color vision. When a color is removed from white light we see the complementary color. The following table shows the colors seen when a complementary color is removed (for example, by a color filter).

Wavelength (Angstroms) Removed

Color Removed

Color Seen (Complementary color)

  • 6800
  • 6100
  • 5800
  • 5600
  • 5300
  • 5000
  • 4800
  • 4300
  • 4100
  • Red
  • Orange
  • Yellow
  • Lemon Yellow
  • Green
  • Blue-green
  • Blue
  • Indigo
  • Violet
  • Blue-green
  • Blue
  • Indigo
  • Violet
  • Purple
  • Red
  • Orange
  • Yellow
  • Lemon Yellow

The yellow strip in the following figure looks yellow because it absorbs indigo light from white light. Indigo is the complementary color of yellow.

A solution containing the complex ion, [Cu(NH3)4]2+, is blue because the complex absorbs red and orange light, the complementary colors of blue and blue-green.

Computer monitors produce colors by producing mixtures of light. For more information, click here.