On 2013–04–18 "H. Özoguz" wrote:

> how to underlay a text (or simply one word) with a (grey) colored
> rectangle, just to highlight – like if I had marked it by hand with
> a grey marker-pen?

\definetextbackground
  [marker]
  [background=color,
   backgroundcolor=yellow,
   frame=off]

\starttext
  \startmarker
    \input knuth
  \stopmarker
  
  \blank
  
  Some \marker{very important} text
\stoptext


Marco