General Chemical Origins
When white light falls upon a sample, the light may be totally reflected, in which case the substance appears white or the light
may be totally absorbed, in which case the substance will appear black. If, however, only a portion of the light is absorbed and
the balance is reflected, the color of the sample is determined by the reflected light. Thus, if violet is absorbed, the sample
appears yellow-green and if yellow is absorbed, the sample appears blue. The colors are described as complementary.
However, many substances which appear colorless do have absorption spectra. In this instance, the absorption will take place in
the infra-red or ultraviolet and not in the visible region. Table 1 illustrates the relationship between light absorption and color.