\starttext

    \definemixedcolumns
      [whatevercolumns]
      [n=2,
       before={\blank[line]},
       after={\blank[line]},
       background=color,
       backgroundcolor=darkred,
       backgroundoffset=.5mm,
       rulethickness=1mm,
       rulecolor=darkgreen,
       color=white,
       separator=rule]

    \input zapf

    \startnarrower
        \startwhatevercolumns
            \input zapf
        \stopwhatevercolumns
    \stopnarrower

    \input zapf

\stoptext
