\setupcolors[state=start]
  \defineenumeration
    [Solution]
    [
      text=Solution,
      number=no,
      headcolor=darkblue,
      headstyle=bold,
      location=serried,
      width=broad,
      before=\blank,
      after=\blank]
  
  \definetextbackground
    [solution]
    [location=paragraph,
     rulethickness=1pt,
     framecolor=red,
     background=color,
     backgroundcolor=lightgray,
     leftoffset=1em,
     topoffset=1em]

  \def\startsolution
    {\startSolution}

 \def\stopsolution
  {\stopSolution}

\starttext

\startsolution
  \input tufte \endgraf
  \midaligned{
  \externalfigure{}
  }
\stopsolution


\stoptext