Color chapter title background (paperwidth)

Question

I want to color background of chapter title like this picture.

The color is:

MWE (xelatex):

\documentclass{book}
\usepackage{titlesec}
\usepackage{tikz} % or maybe with tcolorbox package
\usepackage{xepersian} % Last package
\settextfont{Amiri} % This font has been installed with TeX Live
\titleformat{\chapter}[display]
    {\normalfont\fontsize{16}{19.2}\selectfont\bfseries}%
    {\filleft\chaptertitlename\ \tartibi{chapter}}{1ex}%
    {\filright\fontsize{16}{19.2}\selectfont}
\titlespacing*{\chapter}{0pt}{50pt}{2\baselineskip}
\begin{document}
\chapter{آزمایش}


\end{document}

The output of MWE:

Answer 1

Like this?

(3rd version)

%XeTeX
\documentclass[draft]{book}
\usepackage[showframe]{geometry}
\usepackage{changepage}
\usepackage{xcolor}
% \definecolor{fgcol}{rgb}{51,51,255}
\definecolor{fgcol}{HTML}{3333ff}
%\definecolor{fgcol}{rgb}{0,0,1}
%\usepackage{titlesec}
\usepackage[explicit]{titlesec}
%\usepackage{tikz} % or maybe with tcolorbox package
\usepackage{xepersian} % Last package
\settextfont{Amiri} % This font has been installed with TeX Live
% https://tex.stackexchange.com/a/18578/112708
    \newlength{\myl}
    \setlength{\myl}{\textwidth}
    \addtolength{\myl}{-\marginparsep}
    % \the\myl
    \makeatletter
    \newlength{\lmargin}
    \setlength{\lmargin}{\dimexpr\Gm@lmargin}
    \newlength{\rmargin}
    \setlength{\rmargin}{\dimexpr\Gm@rmargin}
    \newlength{\loffset}
    \setlength{\loffset}{\lmargin}
    \newlength{\roffset}
    \setlength{\roffset}{\rmargin}
    \makeatletter
\titleformat{\chapter}[display]
    {\normalfont\fontsize{16}{19.2}\selectfont\bfseries}%
    {\filleft%
      \hspace{\loffset}
      \chaptertitlename\ \tartibi{chapter}}{1ex}%
    {\begin{adjustwidth}{-\lmargin}{-\rmargin}
        \colorbox{fgcol}{\begin{minipage}{\paperwidth}
          %{\myl} % only across body
            \vspace{2em}
          \color{white}
          \filright\fontsize{16}{19.2}\selectfont #1
          \hspace{\roffset}
            \vspace{2em}
        \end{minipage}}\end{adjustwidth}}
\titlespacing*{\chapter}{0pt}{50pt}{2\baselineskip}
\begin{document}
%\newgeometry{margin=0in}
\chapter{آزمایش}
%\restoregeometry
\end{document}