  A gauge-invariant color-charge operator is defined and related to an integral
of the gauge-invariant chromoelectric field over a closed surface. We discuss
the case of a surface all of whose points are a macroscopic distance from a
system of quarks and gluons which it entirely surrounds. When this system of
quarks and gluons forms a hadron or an object composed of hadrons, such as a
nucleus, it is argued that the gauge-invariant color charge enclosed within
this surface must vanish and the system of hadrons in the interior of the
surface must be a color singlet.
