error with specifying color of watermark in draftwatermark package

[Christopher Ryan]

Hello. Using LaTeX in Windows 10.  I tried to explicitly set the color of
the watermark text. I copied a specification from the package
documentation, page 4.  But it gives me an error:   Argument of \c at lor@@rgb
has an extra }.  If I remove that attempted color specification, document
compiles fine. Grateful for any suggestions. Thanks.

MWE
===
\documentclass[11pt]{article}
\usepackage{outlines}
\usepackage{hyperref}
\hypersetup{
     colorlinks=true,
     linkcolor=blue,
     urlcolor=blue}
\usepackage{savetrees}
\usepackage{url}
\usepackage[scale = 3, color={[rgb]{1, 0, 1}}]{draftwatermark}
\SetWatermarkText{foo \\ bar}

\begin{document}

\section{Hello}

Hello, world!

\end{document}
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