# How can I get the correct hyper pdf underline colour and line width?

I'm trying to set a custom colour for hyperref's link underlining. The MWE below shows what I'm doing. But the colour comes out different - it's the same kind of yellow but a different saturation, if I have to guess. I also haven't figured out how to match the line width to the line width I'm using for the section heading underlines.

\PassOptionsToPackage{svgnames,table,dvipsnames}{xcolor}
\documentclass[a4paper,10pt,oneside,DIV=9]{scrartcl}

% Packages
\usepackage{scrlayer-scrpage}
\usepackage[normalem]{ulem}
\usepackage{hyperref}

% demo only
\usepackage{lipsum}
\usepackage{mwe}

% theme colours and lengths
\definecolor{MyThemeColour}{cmyk}{0.10,0.10,1.00,0} % personal yellow

% outdent and underline section headings
\newlength{\mysecnumhang}
\setlength{\mysecnumhang}{30pt}
\renewcommand*{\sectionformat}{%
\makebox[\mysecnumhang][l]{\thesection\autodot\enskip}%
}
\renewcommand{\sectionlinesformat}[4]{%
}
\bgroup\markoverwith{\textcolor{MyThemeColour}{\rule[-0.75ex]{1pt}{1pt}}}\ULon% 2pt 2pt
}

% make the PDF link underlining use my default colour
\hypersetup{%
}
\makeatletter
\Hy@AtBeginDocument{%
\def\@pdfborder{0 0 1}% Overrides border definition set with colorlinks=true
\def\@pdfborderstyle{/S/U/W 2}% Overrides border style set with colorlinks=true
}
\makeatother

\begin{document}
\section{Lipsum}
\lipsum[1]\footnote{\lipsum[2][1-3]}\footnote{\lipsum[3][1-7]

\lipsum[4][1-7]}

\end{document}


(Compiling using lualatex in case that makes a difference.

\PassOptionsToPackage{svgnames,table,dvipsnames,rgb}{xcolor}
`