\setuppagenumber[state=stop]
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\framed[foregroundcolor=ghost,background=color,backgroundcolor=black]
{Transparent text,\starttextcolor[red] still active here!\stoptextcolor\blackrule[color=blue,width=5cm,height=\strutheight]}
\framed[foregroundcolor=white,background=color,backgroundcolor=black]
{\starttextcolor[ghost]Transparent text,\stoptextcolor\starttextcolor[red] still active here!\stoptextcolor\blackrule[color=blue,width=5cm,height=\strutheight]}
\stoptext
