[NTG-context] Adjust rule between columns

Dear list, Is there a way to adjust the vertical rule which is set between columns? I tried the obvious keys, but they do nothing. \starttext \startcolumns [ n=2, rule=on, rulecolor=red,% does nothing rulethickness=5pt,% does nothing ] \input knuth \stopcolumns \stoptext Furthermore, is there a possibility to control the appearance of the rule per column as in the following (fictitious) commands? \setupcolumns[1][rulecolor=red,rulethickness=5pt] \setupcolumns[2][rulecolor=green,rulethickness=1pt] Cheers, Henri