Thus any color can be specified by a triad of
numbers called Tristimulus Values, or XYZ
values (see Eq. 1). The details can be found in
references [1] and [4]. An easier explanation can
be a color is matched by the amounts of standard
red, green, and blue lights by a normal color
vision observer under a particular standard illuminant. These are the integration of the products of
the functions in three components over the visible
spectrum, say 380 to 700 nm.