In the latest context version of 2006-06-7 coloring the background seems broken.Reverting to the version 2006-05-28 remedied this, but I have no intention of course, to freeze my system at that point.
Here is a minimal example that colors the background in 2006-05-28 and does not in 2006-06-07:
\setupcolors[state=start]
\definetextbackground[showbkg][frame=off,location=text,
background=color,backgroundcolor=orange,backgroundoffset=0pt]
\starttext
tekst \startshowbkg background \stopshowbkg{} tekst.
\stoptext
Can someone look into this? I am relying on this coloring!