why this happens:

After a specification of the foregroundcolor  the figures are  behind a
framed color.

\setupframed[offset=2mm,
     corner=round,
     background=color,
     backgroundcolor=blue,
     foregroundcolor=yellow,
     frame=off,
     strut=no,
     align=normal, location=top,
     width=\textwidth]

For example, is this case my \placefigure[right,nonumber,2*hang]
{}{\externalfigure[ostrichhead][width=5cm]} is behind a yellow framed
rectangle.

Jorge