%this is the way to redefine styles
    % \newpsstyle{mytickstyle}{linewidth=1pt,linecolor=blue}
    %
    \renewcommand{\betweenticks}{100}
    \renewcommand{\shownumbers}{0}
    \newpsstyle{diagframestyle}{linewidth=1pt,linecolor=black,fillcolor=yellow}
    \bardiagrambegin{15}{1000}{2cm}{1}{3}{1cm}{0.015cm}
       \drawlevellines
       \baritem{}{721}{\onecol}
        \subbaritem{Jelger}{500}{\twocol}
       \baritem{}{412}{\onecol}
        \subbaritem{Johan}{500}{\twocol}
       \baritem{}{810}{\onecol}
        \subbaritem{Rikkert}{500}{\twocol}
       \baritem{}{310}{\onecol}
        \subbaritem{Henk}{500}{\twocol}
       \baritem{}{0}{\onecol}
        \subbaritem{New Guy}{542}{\twocol}  
       %
       % we can call
       \diagLegendoptions{yellow}{yellow}{0.0pt}
       % to produce a legend with yellow background with yellow frame
       %
       \diagLegendbegin{10}{890}{3.5}
         \diagLegenditem{19.12.2002}{\onecol}
         \diagLegenditem{06.05.2003}{\twocol}
       \diagLegendend
    \bardiagramend{\large Cluster Users}{\large Jobs Submitted}