How to make colorised linked pagenumbering of appended documents?

Question

I am trying to understand the last part of the answer, Key-value interface's pagenumbering, in the thread How to generate TOC by custom labels at appended documents' beginnings? I would like to colorise the pagenumber to red and make a link to it, back to the first page of the document (ToC, for instance). I think fancypagestyle is not the optimal here in the thread How to label all pagenumbers to TOC in fancy footer? My proposal but sure how to apply them to the Christian's Key-value interface's pagenumbering

• \usepackage{xcolor} so {\color{red} pagenumber}

• with a link to ToC, the following pseudocode, but not sure how to make an internal one here

  \href{some-how-link-to-1st-page-of-document}{{\color{red} pagenumber}}
  

Relevant part of Christian's code

% https://tex.stackexchange.com/a/365580/13173
\usepackage{pdfpages}
\usepackage{hyperref} % for links in TOC
% https://tex.stackexchange.com/q/56316/13173
\usepackage{fancyhdr}
\renewcommand{\headrulewidth}{0pt} % Werner, remove top margin border
% https://tex.stackexchange.com/a/338919/13173
\usepackage{letltxmacro}

\makeatletter
\LetLtxMacro\pdfpages@@includepdf\includepdf

\RenewDocumentCommand{\includepdf}{O{}mo}{%
  \begingroup
  \IfValueTF{#3}{% Is there a 3rd argument? Yes
    % Process the keys for the \includepdf first in order to get the value of 'pages=...' option
    % This is stored to \AM@pagestemp (see pdfpages.sty)
    \setkeys{pdfpages}{#1}%
    \SetupPdfInclude{label={label#2\AM@pagestemp},page={\AM@pagestemp}, heading={#2},#3}
    % Call the old command with the options for addtotoc
    \pdfpages@@includepdf[pagecommand={\thispagestyle{fancy}},addtotoc={\retrieveoption{page},\retrieveoption{section},\retrieveoption{level},\retrieveoption{heading},\retrieveoption{label}},#1]{#2}
  }{% No, no 3rd. argument}
    \pdfpages@@includepdf[pagecommand={\thispagestyle{fancy}},#1]{#2}
  }%
  \endgroup% Prevent leaking of key values to the next call of the command
}
\makeatother

OS: Debian 8.7
Hardware: Asus Zenbook UX303UB

Answer 1

Try a \hypersetup{linkcolor}{red}\hyperlink{mytoc\jobname}{\thepage}} (whereas red is the default colour anyway for links)`

Since this occurs in a group, \hypersetup does not leak outside other than the local group.

\documentclass{article}
\usepackage{blindtext}
\usepackage{fancyhdr}
\usepackage{xcolor}
\usepackage[colorlinks]{hyperref} % for links in TOC
\renewcommand{\headrulewidth}{0pt} 

\fancypagestyle{plain}{%
  \fancyhf{}
  \fancyfoot[L]{\hypersetup{linkcolor=blue}\hyperlink{docstart\jobname}{First page}}
  \fancyfoot[C]{\hypersetup{linkcolor=red}\hyperlink{mytoc\jobname}{\thepage}}
}

\begin{document}
\pagestyle{plain}
\phantomsection
\hypertarget{docstart\jobname}{}
\blindtext[10]
\phantomsection
\hypertarget{mytoc\jobname}{}
\tableofcontents
\clearpage


\section{Beginning Foo}
\blindtext[10]

\end{document}

With fancy pagestyle:

\documentclass{article}
\usepackage{blindtext}
\usepackage{fancyhdr}
\usepackage{xcolor}
\usepackage[colorlinks]{hyperref} % for links in TOC
\renewcommand{\headrulewidth}{0pt} 

% Now for fancy pagestyle
\fancyhf{}
\fancyfoot[L]{\hypersetup{linkcolor=blue}\hyperlink{docstart\jobname}{First page}}
\fancyfoot[C]{\hypersetup{linkcolor=red}\hyperlink{mytoc\jobname}{\thepage}}

\begin{document}
\pagestyle{fancy}
\phantomsection
\hypertarget{docstart\jobname}{}
\blindtext[10]
\phantomsection
\hypertarget{mytoc\jobname}{}
\tableofcontents
\clearpage


\section{Beginning Foo}
\blindtext[10]

\end{document}