titleps multiple headers does not accept rule changes

titleps multiple headers does not accept rule changes

I want to use several different headers and footers in a document. After a
lot of trying I have decided to use titleps as the way to go, as I in any
case redefine the sections, subsections, etc.
The problem is that I have to move the footrule up, because I have the
requirement to add bits that are spread over two lines.
I found that if I use only one page style the redefinition of head- or
footrule works, but one must apparently place it after one have selected a
pagestyle else its not defined.
Here is an MWE:
\documentclass{article}
\usepackage{xcolor}
\usepackage{titleps}
\newpagestyle{a}
{\sethead{}{Header-a}{}\headrule
\setfoot{}{Footer-a}{}\footrule}
\pagestyle{a}
\newpagestyle{b}
{\sethead{}{\parbox{0.4\textwidth}{\centering
Header-b\\Second line}}
{}\headrule
\setfoot{}{\parbox{0.4\textwidth}{\centering
Footer-b\\Second line}}
{}\footrule}
%\pagestyle{b}
\renewcommand\makeheadrule{\color{red}\rule[-1\baselineskip]{\linewidth}{0.4pt}}
\renewcommand\makefootrule{\color{green}\rule[1.2\baselineskip]{\linewidth}{0.8pt}}
\begin{document}
\pagestyle{a}
Page 1
\clearpage
\pagestyle{b}
Page 2
\end{document}
With this I get different headers/footers, but the redefinition of the
head/footrule has no effect.
How could one achieve that?
I would only need one definition of it as it would be common to my whole
document, but in general there could also be the requirement to change it
per pagestyle.