\documentclass[25pt,landscape]{foils}
\usepackage[pdftex,dvipsnames]{color}

\usepackage{geometry}
\usepackage[display]{texpower}

\geometry{headsep=3ex,hscale=0.9}

\renewcommand{\labelitemi}{\textcolor{red}{\origmath{\bullet}}}
\renewcommand{\labelitemii}{\textcolor{yellow}{--}}
\renewcommand{\labelitemiii}{\textcolor{green}{\origmath{\ast}}}
\renewcommand{\labelitemiv}{\textcolor{black}{\origmath{\circ}}}

\MyLogo{Bullet Example}

\begin{document}
\foilhead{Setting the bullets}
\begin{itemize}
\item Level I

\begin{itemize}
\item Level II

\begin{itemize}
\item Level III

\begin{itemize}
\item Level IV
\end{itemize}

\end{itemize}

\end{itemize}

\end{itemize}
\end{document}