[Tex/LaTex] How to color background header

Question

Hi!!I have made this header but I can't set the colors in the background. I'm new in Latex and I find it very difficult. Could anyone help me please??

My work is that:

\documentclass[14pt,a4paper,twoside]{book}
\usepackage[T1]{fontenc}
\usepackage{titlesec, color}
\usepackage{theorem}
\newtheorem{worked example}{Worked Example}[chapter]
\newtheorem{solution}{SOLUSION}[chapter]
\usepackage{anyfontsize}
\usepackage{amsfonts}
\usepackage{textcomp}
\usepackage{enumerate}
\usepackage{fancyhdr}
\pagestyle{fancy}

\fancyhead{}
\renewcommand{\chaptermark}[1]{\markboth{\textbf{\thechapter \ | \ #1}}{}}
\fancyhead[LE]{\hspace{30pt}\textbf{\thepage} \hspace{20pt} \leftmark}
\renewcommand{\sectionmark}[1]{\markright{\textbf{\thesection \ | \ #1}}}
\fancyhead[RO]{\rightmark \hspace{20pt} \textbf{\thepage} \hspace{30pt}}
\fancyfoot{}
\addtolength{\headwidth}{\marginparsep}
\addtolength{\headwidth}{\marginparwidth}
\renewcommand{\headrulewidth}{}
\renewcommand{\footrulewidth}{}

\setlength\headheight{50pt}

\newcommand{\hsp}{\hspace{20pt}}
\newcommand{\ntl}{\newline \newline}

\titleformat{\chapter}[hang]{\fontsize{50}{60}\bfseries\color[rgb]{0,0.5,0.75}}{\thechapter\hsp\fontsize{90}{60}\selectfont\textcolor{black}{|}\hsp}{0pt}{\Huge\bfseries}

\titleformat{\section}{\large\bfseries}{}{0pt}{\textcolor[rgb]{0,0.5,0.75}{Topic \thesection} \ }[{\titlerule[0.8pt]}]

\begin{document}
\chapter{\textcolor{black}{NUMBER}}
\section{BIDMAS.}
\thispagestyle{empty}
.
.
.
.
.
\end{document}

Answer 1

Here is solution with titleps, in the place of fancyhdr: just load titlesec with option pagestyles. You won't have to fight with marks: just use \sectiontitle and \chaptertitle when you define a new pagestyle. \thispagestyle{empty} may very well be incorporated into \titleformat[\chapter}, it will save typing it at each new chapter.

\documentclass[14pt,a4paper,twoside]{extbook}
\usepackage[utf8]{inputenc} %
\usepackage[T1]{fontenc}
\usepackage{lmodern} %
\usepackage[pagestyles]{titlesec}
\usepackage[x11names]{xcolor} %
\usepackage{theorem}
\newtheorem{worked example}{Worked Example}[chapter]
\newtheorem{solution}{SOLUTION}[chapter]
%\usepackage{anyfontsize}
\usepackage{amsfonts}
\usepackage{textcomp}
\usepackage{enumerate}
\setlength\headheight{21pt}

\newcommand{\hsp}{\hspace{20pt}}
\newcommand{\ntl}{\newline \newline}

\titleformat{\chapter}[hang]{\fontsize{50}{60}\bfseries\color[rgb]{0,0.5,0.75}}{\thechapter\hsp\fontsize{90}{60}\selectfont\textcolor{black}{|}\hsp}{0pt}{\thispagestyle{empty}\Huge\bfseries}

\titleformat{\section}{\large\bfseries}{}{0pt}{\textcolor[rgb]{0,0.5,0.75}{Topic \thesection} \ }[{\titlerule[0.8pt]}]

\usepackage{blindtext}

\newpagestyle{mine}{%
\setlength\fboxsep{10pt}
\sethead[\bfseries\llap{\colorbox{SteelBlue3}{\parbox{\dimexpr\marginparsep + \marginparwidth\relax}{\hspace{20pt}\color{white}\thepage\vphantom{|}}}}%
\colorbox{SlateGray2!40}{\parbox{\dimexpr\linewidth-2\fboxsep}{~\thechapter~|\hspace{0.75em}\chaptertitle}}][][]%
{}{}{\bfseries\colorbox{SlateGray2!40}{\parbox{\dimexpr\linewidth-2\fboxsep}{\thesection~|\hspace{0.75em}\sectiontitle}}%
\rlap{\colorbox{SteelBlue3}{\parbox{\dimexpr\marginparsep + \marginparwidth\relax}{\hspace{20pt}\color{white}\thepage\vphantom{|}}}}}
\setfoot{}{}{}
}

\pagestyle{mine}

\begin{document}

\chapter{{NUMBER}}%\textcolor{black}
\section{BIDMAS.}
\blindtext[10]

\end{document}