The answer to my question is
\usepackage{color}.
Sorry to have bothered everybody.
--
Kevin Cahill Phone: 505 277 5318
Department of Physics and Astronomy Fax: 505 277 1520
University of New Mexico Web page: kevin.phys.unm.edu/~kevin/
Albuquerque, NM 87131-1156 E-mail: cahill at unm.edu