Hello,
In the code below, the red vertical line extends beyond the edges of the
cell.
Thank you
Fabrice

\startuniqueMPgraphic{Vertical}

  linecap:=squared ;
  path p ; p := unitsquare xyscaled (OverlayWidth,OverlayHeight) ;
  drawoptions (withpen pencircle withcolor \MPcolor{red}) ;
  draw .5[llcorner p, lrcorner p]--.5[ulcorner p, urcorner p] ;
  setbounds currentpicture to p ;

\stopuniqueMPgraphic

\defineoverlay[Vertical][\uniqueMPgraphic{Vertical}]

\startsetups[table:initialize]

\setupTABLE[start]
           [align={middle,lohi},offset=0.5ex,width=1.5cm,
            foregroundstyle={\switchtobodyfont[10pt]}]
\setupTABLE[1][2][background=Vertical]

\stopsetups

\starttext
\startlinecorrection[blank]
  \startmidaligned
    \bTABLE[setups=table:initialize]
    \bTR
    \bTD \math{\red 0 {\rm (A)}} \eTD
    \bTD \math{+\infty}          \eTD
    \eTR
    \bTR
    \bTD                         \eTD
    \bTD  \math{+\infty}         \eTD
    \eTR
    \eTABLE
  \stopmidaligned
\stoplinecorrection
\stoptext