However with the snippet below I see the default black with MPcolor and the wanted red with \MPvar. Thus?
Hans van der Meer
\starttext
\startuseMPgraphic{example1}{color}
pickup pencircle scaled 1mm;
draw unitsquare scaled 1cm
withcolor \MPcolor{color};
\stopuseMPgraphic
\startuseMPgraphic{example2}{color}
pickup pencircle scaled 1mm;
draw unitsquare scaled 1cm
withcolor \MPvar{color};
\stopuseMPgraphic
\useMPgraphic{example1}{color=red}
\useMPgraphic{example2}{color=red}
\stoptext