% output=pdftex

\setupcolors[state=start]

\startuniqueMPgraphic{CoCircle}
   fill fullcircle xysized (OverlayWidth,OverlayHeight) withcolor OverlayColor ;
\stopuniqueMPgraphic
 
\defineoverlay[cocircle][\uniqueMPgraphic{CoCircle}]
 
\definecolor[CoBackgroundColor] [red]
\definecolor[CoForegroundColor] [white]
 
\def\conum#1%
   {\setbox\scratchbox\hbox
      {\small\ss\bf
       \setbox\scratchbox\hbox{99}%
       \hbox to 1.2\wd\scratchbox{\hss#1\hss}}%
    \framed
      [background=cocircle,
       offset=overlay,
       frame=off,
       width=\the\wd\scratchbox,
       height=\the\wd\scratchbox,
       backgroundcolor=CoBackgroundColor,
       foregroundcolor=CoForegroundColor]
      {\box\scratchbox}}
 
\starttext
  \dontleavehmode \dorecurse{99}{\conum{\recurselevel}, }
\stoptext
