Consider the following minimum working example containing a blockquote
as defined in a Pandoc-generated document:
\setuppapersize [A4][A4]
\setuplayout [width=middle, backspace=1.5in, cutspace=1.5in,
height=middle, topspace=0.75in, bottomspace=0.75in]
\setuppagenumbering[location={footer,center}]
\setupdelimitedtext
[blockquote]
[before={\blank[medium]},
after={\blank[medium]},
indentnext=no,
]
\starttext
\input tufte
\startblockquote
\input zapf
\stopblockquote
\input knuth
\stoptext
Question
How could I obtain a light gray background for the blockquote
with a dark red 1em-thick left vertical borderline only by changing the preamble?
Other borders should be 0pt.