Hi,
I encounter two problems :
- Section numbers are not red ;
- Calling the second section does not cause the creation of a new paragraph.
Regards,
Fabrice

\setupcolors[state=start]
\def\MySectionCommand#1#2%
  {\framed
     [frame=off,
      width=\textwidth,
      align={right},
      background=color,
      backgroundcolor=lightgray]
     {#1\quad#2}}

\setuphead[section][command=\MySectionCommand,numbercolor=red]

\setupbodyfont[palatino,12pt]

\starttext

\MySectionCommand{A.}{Définitions}
\input knuth
\MySectionCommand{1.}{Propriétés}
\input knuth

\setupcolors[state=start]
\define[2]\MySectionCommand
  {\framed
     [frame=off,
      width=\textwidth,
      align={right},
      background=color,
      backgroundcolor=lightgray]
     {#1.\quad#2}}

\setuphead[section][command=\MySectionCommand,ownnumber=yes,numbercolor=red]

\setupbodyfont[palatino,12pt]

\starttext

\placecontent

\section{A}{Définitions}
\input knuth

\section{1}{Propriétés}
\input knuth

\section{2}{Propriétés}
\input knuth

\section{3}{Propriétés}
\input knuth

\section{B}{Définitions}
\input knuth

\section{1}{Propriétés}
\input knuth

\section{2}{Propriétés}
\input knuth

\stoptext