Package xcolor Error: Undefined color `gold'

Question

When I compile this document using pdflatex, my chapter's (and sections and subsections, too) titles are, respectively, blue (here defined as 'azzurro') and gold.

I would like that all titles and subtitles be black.

This is the document:

    \documentclass[envcountsame,envcountchap]{svmono}

    %\usepackage[latin1]{inputenc}
     \usepackage[utf8]{inputenc}
     \usepackage{eurosym}
    \usepackage{makeidx}                % allows index generation
    \usepackage{graphicx}               % standard LaTeX graphics tool
    \usepackage{xtab}                   % when including figure files
    \usepackage{multicol}
    \usepackage{qtree}
    \usepackage{booktabs}
    \usepackage{latexsym}
     \usepackage{psfig}                  % used for the two-column index
     \usepackage[bottom]{footmisc}       % places footnotes at page bottom
    \usepackage[italian]{babel}
    \usepackage{my_listings}
    \usepackage[hyphens]{url}
    \usepackage{algorithm}
    \usepackage{algorithmic}
    \usepackage{multirow}
    \usepackage{xcolor}
    \usepackage{float}
     \usepackage{titlesec}
      \usepackage{csquotes}
       \usepackage{python}
      \usepackage{verbatim}
      \usepackage{eurosym}
      \usepackage[figuresright]{rotating}
     \usepackage{pdflscape}
\usepackage{tcolorbox}
%\setcounter{secnumdepth}{3}
%\setcounter{tocdepth}{3}
\makeatletter
\titleformat{\section}[display]%
  {\Large\bfseries\boldmath}{\color{azzurro}{\thesection}}{-1.1em}{\hspace{2em}\color{azzurro}}[{\titlerule[0pt]}]
\makeatother

\makeatletter
\titleformat{\subsection}[display]%
  {\large\bfseries\boldmath}{\color{gold}{\thesubsection}}{-1em}{\hspace{3em}\color{gold}}[{\titlerule[0pt]}]
\makeatother

\makeatletter
\titleformat{\subsubsection}[display]%
  {\normalsize\bfseries\boldmath}{\color{gold}{\thesubsubsection}}{-1em}{\color{gold}}[{\titlerule[0pt]}]
\makeatother

\definecolor{gold}{rgb}{0.64,0.54,0.29}
\definecolor{azzurro}{rgb}{0,0.29,0.57}

\def\lstlistlistingname{\textbf{Elenco dei listati}}
\addto\captionsitalian{\renewcommand{\contentsname}{\textbf{Indice}}}
\addto\captionsitalian{\renewcommand{\listfigurename}{\textbf{Elenco delle figure}}}


\makeatletter
\let\old@rule\@rule
\def\@rule[#1]#2#3{\textcolor{gold}{\old@rule[#1]{#2}{#3}}}
\makeatother

\setlength{\textwidth}{12.7cm}
\setlength{\textheight}{20.0cm}
\setlength{\oddsidemargin}{3.50cm}
\setlength {\evensidemargin}{-0.3cm}
\setlength {\topmargin}{-1cm}


\makeindex

\author{}

\date{13 marzo 2018}

\begin{document}


\pagenumbering{{\color{azzurro}Roman}}
%\include{frontespizio/frontespizio}
%\newpage\null\thispagestyle{empty}\newpage
%\include{dedica/dedica}
%\tableofcontents \listoffigures
%\lstlistoflistings

\pagenumbering{arabic} \setcounter{page}{1}

%\include{Introduzione/introduzione}
\include{01-IlCrowdsourcing/capitolo-01}
%\include{02-LaSentimentAnalysis/capitolo-02}
%\include{03-ProgettazioneDeiTaskDiBase/capitolo-03}
%\include{04-ImplementazioneDeiTaskDiBaseERisultati/capitolo-04}
%\include{05-ProgettazioneDeiTaskAvanzati/capitolo-05}
%\include{06-ImplementazioneDeiTaskAvanzatiERisultati/capitolo-06}
%\include{07-ConfrontoConApprocciCorrelati/capitolo-07}
%\include{08-DiscussioneInMeritoAll'attivitàSvolta/capitolo-08}

\nocite{*}
%\bibliography{Bibliografia/biblio}
\bibliographystyle{plain}
%\include{Ringraziamenti/ringraziamenti}
\end{document}

In this way the file is compiled like the attached image.

When I replace the colors with 'black' as

\definecolor{black}{rgb}{0,0,0}

it give me these errors:

Package xcolor Error: Undefined color gold

Package xcolor Error: Undefined color azzurro

What I can do?

Answer 1

Observe that you are using \color{azzurro} (twice: one for counter and other for title) in the definition of \subsection.

\makeatletter
\titleformat{\section}[display]%
  {\Large\bfseries\boldmath}{\color{azzurro}{\thesection}}{-1.1em}{\hspace{2em}\color{azzurro}}[{\titlerule[0pt]}]
\makeatother

So just replace azurro by black or even better delete \color{azzurro}, since black is the default color.

Do the same in the definition of \subsection.

A bad but faster solution would be to keep the definitions and just change RGB values to the color namedazurro, ie, \definecolor{azzurro}{rgb}{0,0,0}. With that you will get a black azurro.

Finally, the error Package xcolor Error: Undefined color gold you got was because you had changed the name of the defined color (gold by black) but you were still using the gold color in codes above. This is why undefined color error.