Added some separate examples.

examples/externalize.tex

@@ -0,0 +1,43 @@
+% comment out to define
+%\def\CompileTikZFigures{}
+
+\documentclass{article}
+\usepackage{xspace}
+\usepackage{tikz}
+\ifx\CompileTikZFigures\undefined
+	\usetikzlibrary{external}
+	\tikzexternalize[prefix=pics/tikz/]
+\fi
+
+\usepackage{todonotes}
+
+\ifx\CompileTikZFigures\undefined
+	\makeatletter
+	\renewcommand{\todo}[2][]{%
+		\tikzexternaldisable%
+		\@bsphack\@todo[#1]{#2}\@esphack\ignorespaces%
+		\tikzexternalenable%
+		\xspace%
+		}
+	\makeatother
+\else
+	\makeatletter
+	\renewcommand{\todo}[2][]{%
+		\@bsphack\@todo[#1]{#2}\@esphack\ignorespaces\xspace%
+	}
+	\makeatother
+\fi
+
+\begin{document}
+Example by Marek Rjelka.
+
+\verb+\CompileTikZFigures+ is
+\ifx\CompileTikZFigures\undefined%
+	un%
+\fi%
+defined.
+
+\bigskip
+Here goes some\todo{a comment} text.
+
+\end{document}

examples/saveColorByUsingLayers.tex

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+\documentclass{article}
+\usepackage{todonotes}
+\usepackage{ocg-p}
+\newcommand{\TODO}[1]{
+\newsavebox\todoboxa
+\savebox\todoboxa{\begin{ocg}[printocg=never]{ToDo screen}{todo4screen}{1}
+\todo[inline]{#1}
+\end{ocg}}
+\newsavebox\todoboxb
+\savebox\todoboxb{\begin{ocg}[printocg=always]{ToDo print}{todo4print}{0}
+\todo[inline, color=white]{#1}
+\end{ocg}}
+\noindent\usebox\todoboxb\llap{\usebox\todoboxa}
+\global\let\todoboxa\relax
+\global\let\todoboxb\relax
+}
+
+\begin{document}
+
+\section{Hello world!}
+
+The todo inserted below is shown in color on the screen, but in black and white when sent to the printer.
+
+Example by Robert Rehner.
+
+\TODO{Example todo}
+\end{document}