\colwidths{{50pt}{60pt}{70pt}{80pt}}

\def\cals@borderT{2pt}
\def\cals@borderR{4pt}
\def\cals@borderB{6pt}
\def\cals@borderL{8pt}
\def\cals@bgcolor{red}
\cals@decor@begin
\nullcell{ltb}
\nullcell{tb}
\nullcell{}
\nullcell{tbr}
\cals@decor@end\cals@lastWidth
\showbox\cals@current@cs
\show\cals@current@rs@above
\show\cals@current@rs@below

\def\cals@borderT{1pt}
\def\cals@borderR{3pt}
\def\cals@borderB{5pt}
\def\cals@borderL{7pt}
\def\cals@bgcolor{green}
\cals@decor@begin
\nullcell{ltb}
\nullcell{}
\nullcell{tb}
\nullcell{tbr}
\cals@decor@end\cals@lastWidth
\showbox\cals@current@cs
\show\cals@current@rs@above
\show\cals@current@rs@below