[texhax] xcolor package puzzle

[Thomas Schneider]

Dear TexHax and James Allison:

I am preparing a paper for PNAS.  The PNAS class file pnas-new.cls has
\RequirePackage{xcolor}.

For a table I am working on I have been using the table flag:

\usepackage[table]{xcolor}

so that I can get alternating grey striped lines:

\colorlet{tablerowcolor}{gray!19.0}
\rowcolors{4}{white}{tablerowcolor} % start alternation on 4th row

However, my usepackage conflicts with the PNAS cls file.  I could
modify the pnas-new.cls file but then it would fail when PNAS folks
compile my document with their standard cls.

Is there a way to activate [table] for xcolor so that I can use it?

----

The manual for xcolor says "These commands require the table option
(which loads the colortbl package)" (page 28).   Although I can
\usepackage{colortbl}, I still get 'Undefined control sequence' for
\rowcolors.  So that doesn't work ...

Tom

  Thomas D. Schneider, Ph.D.
  Senior Investigator
  National Institutes of Health
  National Cancer Institute
  Center for Cancer Research
  RNA Biology Laboratory
  Biological Information Theory Group
  Frederick, Maryland  21702-1201
  schneidt at mail.nih.gov
  https://alum.mit.edu/www/toms