documentclass[12pt]{report}
usepackage[usenames,dvipsnames]{color}%need colors
usepackage{pdfpages}
...
begin{document}
...
textcolor{OliveGreen}{green}
...
includepdf{AppendixChapter3.pdf}
...
end{document}

! LaTeX Error: Option clash for package color.

See the LaTeX manual or LaTeX Companion for explanation.
Type  H <return>  for immediate help.
 ...

l.8 newcommand
           *{mycommand}[1]{texttt{emph{#1}}}