% tex.stackexchange.com/questions/557511/…?
\begin{filecontents*}{IfFileHasChanged.tex}
\RequirePackage{expl3}
\ExplSyntaxOn
\file_if_exist:nTF { myfile.txt }
  {
    \ior_open:Nn \g_tmpa_ior { myfile.txt }
    \ior_str_get:NN \g_tmpa_ior \l_tmpa_tl
    \ior_close:N \g_tmpa_ior
    \tl_put_right:Nn \l_tmpa_tl { ~change. }
  }
  { \tl_set:Nn \l_tmpa_tl { This~is~my~file. } }
\iow_open:Nn \g_tmpa_iow { myfile.txt }
\iow_now:Nx \g_tmpa_iow { \l_tmpa_tl }

\ExplSyntaxOn
\cs_new:Npx \__color_split_colon:n #1
  {
    \exp_not:N \__color_split_colon:w  #1 \c_colon_str \c_colon_str
    \exp_not:N \q_stop
  }
\use:x
  {
    \cs_new:Npn \exp_not:N \__color_split_colon:w ##1 \c_colon_str ##2 \c_colon_str
    ##3 \exp_not:N \q_stop
  }
  {
    \tl_if_blank:nTF {#2}
      { #1 }
      { #2 }
  }
\cs_set_protected:Npn \test #1
  {
    \tl_set:Nx \l_tmpa_tl { \__color_split_colon:n { #1 } }
    \tl_show:N \l_tmpa_tl
  }
\ExplSyntaxOff
\test{rgb}
\test{rgb/cmyk}

% Check if Raw Data has changed
\input{IfFileHasChanged.tex}
\IfFileChangedTF{\PersDataRawFilename}
       {\MakePersDataHelpfile}
          {  \IfFileExists{\PersDataHelpFilename}{}{\MakePersDataHelpfile}  }

\ExplSyntaxOn
\cs_if_exist:NT \color_set:nnn
   {
    \cs_new_protected:Npn \@expl@color@set@nnn #1#2#3
     { \exp_args:Nnx\color_set:nnn {#1}{\__color_split_colon:n { #2 }}{#3}}
   }
\pretocmd{\XC@definec@lor}{\def\tmpa{#1}\show\tmpa\@expl@color@set@nnn{#2}{#4}{#5}}{}{\fail}
\ExplSyntaxOff

% Check if Raw Data has changed

\IfFileChangedTF{\PersDataRawFilename}
       {\MakePersDataHelpfile}
          {  \IfFileExists{\PersDataHelpFilename}{}{\MakePersDataHelpfile}  }

% tex.stackexchange.com/questions/557511/…?
\begin{filecontents*}{IfFileHasChanged.tex}
\RequirePackage{expl3}
\ExplSyntaxOn
\file_if_exist:nTF { myfile.txt }
  {
    \ior_open:Nn \g_tmpa_ior { myfile.txt }
    \ior_str_get:NN \g_tmpa_ior \l_tmpa_tl
    \ior_close:N \g_tmpa_ior
    \tl_put_right:Nn \l_tmpa_tl { ~change. }
  }
  { \tl_set:Nn \l_tmpa_tl { This~is~my~file. } }
\iow_open:Nn \g_tmpa_iow { myfile.txt }
\iow_now:Nx \g_tmpa_iow { \l_tmpa_tl }

% tex.stackexchange.com/questions/557511/…?
\begin{filecontents*}{IfFileHasChanged.tex}
\RequirePackage{expl3}
\ExplSyntaxOn
\file_if_exist:nTF { myfile.txt }
  {
    \ior_open:Nn \g_tmpa_ior { myfile.txt }
    \ior_str_get:NN \g_tmpa_ior \l_tmpa_tl
    \ior_close:N \g_tmpa_ior
    \tl_put_right:Nn \l_tmpa_tl { ~change. }
  }
  { \tl_set:Nn \l_tmpa_tl { This~is~my~file. } }
\iow_open:Nn \g_tmpa_iow { myfile.txt }
\iow_now:Nx \g_tmpa_iow { \l_tmpa_tl }