Different colors for each bib file and custom prefix

Question

I have multiple bib files. I would like to use different text colors for all the references mentioned in different bib files. Secondly, i would like a custom prefix for each bib file.

Please let me know how can I do it?

The result should be similar to as follows:

[R1] uses [O1] and [R2] is based on [O2].

References

[R1] .....

[R2] .....

Other References

[O1] ....

[O2] ....

Color of references mentioned in section "References" will be black, where as color of references mentioned in section "Other references" will be blue.

Answer 1

We can split the bibliography by .bib file (something that is not necessarily very semantic) following biblatex: multiple bibliographies categorised by different .bib files and separating bibliography items based on resource file (the second link shows how to deal with existing keywords).

Adding the additional letter into the label is then as simple as issuing \newrefcontext[labelprefix=<prefix>] before the \printbibliography. See Biblatex entry renumbering and prefixing, Custom citation label, Biblatex with sections, prefix, and reversed order, Separate bibliographies for phdthesis and mastersthesis in biblatex.

\documentclass{article}

\usepackage{xcolor}
\usepackage[backend=biber, style=numeric, defernumbers]{biblatex}

\DeclareSourcemap{
  \maps[datatype=bibtex,overwrite]{
    \map{
      \perdatasource{\jobname-1.bib}
      \step[fieldset=keywords, fieldvalue={,file1}, append]
    }
    \map{
      \perdatasource{\jobname-2.bib}
      \step[fieldset=keywords, fieldvalue={,file2}, append]
    }
  }
}

\newcommand*{\mkbibcolourcite}[1]{%
  \ifkeyword{file2}
    {\textcolor{blue}{#1}}
    {#1}}
\DeclareFieldFormat{labelnumberwidth}{\mkbibbrackets{\mkbibcolourcite{#1}}}
\DeclareFieldFormat{colourcite}{\mkbibcolourcite{#1}}

\renewbibmacro*{cite}{%
  \printtext[bibhyperref]{%
    \printtext[colourcite]{%
      \printfield{labelprefix}%
      \printfield{labelnumber}%
      \ifbool{bbx:subentry}
        {\printfield{entrysetcount}}
        {}}}}

\usepackage{filecontents}
\begin{filecontents}{\jobname-1.bib}
@book{book1,
  author = {Onymous, Anne},
  title  = {First Bibliography: Category 1},
  date   = {2000},
}
@book{book3,
  author   = {Scribbler, Sarah},
  title    = {First Bibliography Again: Category A and B},
  date     = {1899},
  keywords = {cata},
}
\end{filecontents}
\begin{filecontents}{\jobname-2.bib}
@book{book2,
  author = {Writer, William},
  title  = {Second Bibliography: Category 2},
  date   = {2010},
}
@book{book4,
  author = {Poetaster, Paula},
  title  = {Second Bibliography Again: Category B},
  date   = {1767},
}
\end{filecontents}

\addbibresource{\jobname-1.bib}
\addbibresource{\jobname-2.bib}

\begin{document}
\cite{book1,book2,book3,book4}
\newrefcontext[labelprefix=R]
\printbibliography[keyword=file1]
\newrefcontext[labelprefix=O]
\printbibliography[keyword=file2, title=Other references]
\end{document}

edit How embarassing! I completely forgot to colour the citations according to their file/keyword. That is fixed now. Sorry!