Visible light, roughly from 400nm - 750nm
is the only part of the electromagnetic spectrum which is transmitted from the
eye to the brain, which the brain can, in turn, interpret as a picture.

If two electromagnetic radiations have very different in wave-lengths, the radiation will be
of different type. If two rays of visible light differ only slightly in wavelength, they will have different effects on the eye, i.e. they will
appear to be different colors.

Light at any unit wavelength is almost imper-ceptibly different from light at the next unit wavelength so one color merges into the next, hence, the number of
colors is limitless. All the wavelengths are present in sunlight, and the eye recognizes this mixture of wavelengths as the color we call White. When a colored object is illuminated by white light, it selectively absorbs some of the wavelengths and transmits others.

The eye receives the transmitted wavelengths and summarizes them as one color. This color is dominated by the main wavelength transmitted, which determines its basic hue. This hue is modified by undertones from the other wavelengths, which make it an individual shade. A fundamental aspect of color chemistry is how much and at what wavelengths original white light is retransmitted by an object.