\renewcommand{\tdx}{1.2} % depth of 3d
\renewcommand{\tdy}{6}

\def\onecol{red}
\def\twocol{green}
\def\threecol{lightblue}
%-------------------------------------------------------

%this is the way to redefine styles
% \newpsstyle{mytickstyle}{linewidth=1pt,linecolor=blue}
%
\newpsstyle{diagframestyle}{linewidth=1pt,linecolor=black,fillcolor=white}
\bardiagrambegin{14}{100}{3cm}{1}{5}{1cm}{0.1cm}
       \baritem{1990}{72}{\onecol}
        \subbaritem{2000}{50}{\twocol}
        \subbaritem{2010}{63}{\threecol}
       \baritem{1990}{81}{\onecol}
        \subbaritem{2000}{99}{\twocol} 
        \subbaritem{2010}{50}{\threecol}  
       \baritem{1990}{41}{\onecol}
        \subbaritem{2000}{30}{\twocol}
        \subbaritem{2010}{21}{\threecol} 
\bardiagramend{\parbox{14cm}{\vspace{-1.5cm}\hspace{-1cm}
   \begin{tabular}{p{4.5cm}p{4.5cm}p{4.5cm}}
      \centering Alpha's & \centering Beta's & \centering Gamma's
   \end{tabular}
   \\[0.6cm]
   \centering \large Year}}
  {\large Graduated (\%)}