Changing label color for each call of the \chapter command

Question

I would like to change the color of the chapter label (small rectangle box) everytime I call the command \chapter{}, possibly passing the color as an argument.

Thus the part I need to address with the argument is the command \draw[fill=black].

Here a compilable example:

\documentclass{book}
\usepackage{color}
\usepackage{tikz}
\usepackage[explicit]{titlesec}
\newcommand*\chapterlabel{}
%\renewcommand{\thechapter}{\Roman{chapter}}
\titleformat{\chapter}[display]  % type (section,chapter,etc...) to vary,  shape (eg display-type)
{\normalfont\fontsize{24}{26}\bfseries} % format of the chapter
{\gdef\chapterlabel{\thechapter\ }}     % the label 
{0pt} % separation between label and chapter-title
  {\begin{tikzpicture}[remember picture,overlay]
\node[yshift=-8cm] at (current page.north west)
  {\begin{tikzpicture}[remember picture, overlay] 
    \draw[fill=black] (0,0) rectangle(35.5mm,15mm);
    \node[anchor=north east,yshift=-7.2cm,xshift=34mm,minimum height=30mm,inner sep=0mm] at (current page.north west)
    {\parbox[top][30mm][t]{15mm}{\raggedleft $\phantom{\textrm{l}}$\color{white}\chapterlabel}};  %the black l is just to get better base-line alingement
    \node[anchor=north west,yshift=-7.2cm,xshift=37mm,text width=\textwidth,minimum height=30mm,inner sep=0mm] at (current page.north west)
          {\parbox[top][30mm][t]{\textwidth}{\color{black}#1}};
   \end{tikzpicture}
  };
 \end{tikzpicture}
  \gdef\chapterlabel{}
  } % code before the title body
 \usepackage[utf8]{inputenc}
\title{test}
\begin{document}
\maketitle
\chapter{Introduction}
\end{document}

I tried to pass the argument to the \chapterlabel function but didn't work. I also found a very similar question "https://tex.stackexchange.com/questions/641554/change-color-for-each-chapter" that didn't really received an answer (I tried the solution proposed but didn't work).

I would be really greatful if someone can help.

You could define colours with numbers in their names which will correspond to the chapter number. Can you make a small but compilable minimal working example? — samcarter_is_at_topanswers.xyz, Jan 25 '23 at 15:51
@samcarter_is_at_topanswers.xyz thanks for your comment. I added a compilable working example. I'll try to see if I manage to do what you suggest. — 081N, Jan 25 '23 at 16:45

samcarter_is_at_topanswers.xyz · Accepted Answer · 2023-01-25T16:55:10.333

I suggest to define a series of colours with numbers in their names and the chapter will then use the colour depending on the current chapter number:

\documentclass{book}
\usepackage{color}
\usepackage{tikz}
\usepackage[explicit]{titlesec}
\colorlet{chapter1}{red}
\colorlet{chapter2}{blue}
\newcommand*\chapterlabel{}
%\renewcommand{\thechapter}{\Roman{chapter}}
\titleformat{\chapter}[display]  % type (section,chapter,etc...) to vary,  shape (eg display-type)
{\normalfont\fontsize{24}{26}\bfseries} % format of the chapter
{\gdef\chapterlabel{\thechapter\ }}     % the label 
{0pt} % separation between label and chapter-title
  {\begin{tikzpicture}[remember picture,overlay]
\node[yshift=-8cm] at (current page.north west)
  {\begin{tikzpicture}[remember picture, overlay] 
    \draw[fill=chapter\the\value{chapter}] (0,0) rectangle(35.5mm,15mm);
    \node[anchor=north east,yshift=-7.2cm,xshift=34mm,minimum height=30mm,inner sep=0mm] at (current page.north west)
    {\parbox[top][30mm][t]{15mm}{\raggedleft $\phantom{\textrm{l}}$\color{white}\chapterlabel}};  %the black l is just to get better base-line alingement
    \node[anchor=north west,yshift=-7.2cm,xshift=37mm,text width=\textwidth,minimum height=30mm,inner sep=0mm] at (current page.north west)
          {\parbox[top][30mm][t]{\textwidth}{\color{black}#1}};
   \end{tikzpicture}
  };
 \end{tikzpicture}
  \gdef\chapterlabel{}
  } % code before the title body
 \usepackage[utf8]{inputenc}
\title{test}
\begin{document}
\maketitle
\chapter{Introduction}
\chapter{foo}
\end{document}

Alternatively you could colour the chapter with a user defined colour and change its definition before each chapter:

\documentclass{book}
\usepackage{color}
\usepackage{tikz}
\usepackage[explicit]{titlesec}
\colorlet{chapter}{red}
\newcommand*\chapterlabel{}
%\renewcommand{\thechapter}{\Roman{chapter}}
\titleformat{\chapter}[display]  % type (section,chapter,etc...) to vary,  shape (eg display-type)
{\normalfont\fontsize{24}{26}\bfseries} % format of the chapter
{\gdef\chapterlabel{\thechapter\ }}     % the label 
{0pt} % separation between label and chapter-title
  {\begin{tikzpicture}[remember picture,overlay]
\node[yshift=-8cm] at (current page.north west)
  {\begin{tikzpicture}[remember picture, overlay] 
    \draw[fill=chapter] (0,0) rectangle(35.5mm,15mm);
    \node[anchor=north east,yshift=-7.2cm,xshift=34mm,minimum height=30mm,inner sep=0mm] at (current page.north west)
    {\parbox[top][30mm][t]{15mm}{\raggedleft $\phantom{\textrm{l}}$\color{white}\chapterlabel}};  %the black l is just to get better base-line alingement
    \node[anchor=north west,yshift=-7.2cm,xshift=37mm,text width=\textwidth,minimum height=30mm,inner sep=0mm] at (current page.north west)
          {\parbox[top][30mm][t]{\textwidth}{\color{black}#1}};
   \end{tikzpicture}
  };
 \end{tikzpicture}
  \gdef\chapterlabel{}
  } % code before the title body
 \usepackage[utf8]{inputenc}
\title{test}
\begin{document}
\maketitle
\colorlet{chapter}{green}
 \chapter{Introduction}
\colorlet{chapter}{orange} 
  \chapter{foo}
\end{document}

Changing label color for each call of the \chapter command

1 Answers1