\documentclass[headsepline,headheight=28pt]{scrreprt}
%\documentclass[headsepline,headheight=28pt]{scrlttr2}
\usepackage{xcolor}
\usepackage[headsepline=1.9pt]{scrlayer-scrpage}
\addtokomafont{headsepline}{\color{purple}}
\DeclareNewLayer[
clone=scrheadings.head.below.line,
addvoffset=1.9pt,
contents={\KOMAoptions{headsepline=.6pt}%
\GetLayerContents{scrheadings.head.below.line}},
]{scrheadings.head.below.secondline}
\AddLayersToPageStyle{scrheadings}{scrheadings.hea d.below.secondline}
\usepackage{blindtext}
\begin{document}
%\blinddocument
Hier steht der Text, den ich sehen will.
\end{document}
Lesezeichen