\documentclass[17pt,a4paper]{extarticle}
\usepackage{lipsum} % for dummy text
\usepackage{tikz} %  for TikZ drawings
\usepackage{eso-pic} %  for \AddToShipoutPictureBG
\usepackage{fontspec} %  for setting fonts
\usepackage{shapepar} % for shaped paragraphs

\definecolor{crimson}{RGB}{220,20,60}
\colorlet{blueA}{blue!20!cyan!40!white}
\colorlet{blueB}{blue!30!cyan!20!white}
\setmainfont{DejaVu Sans Mono}

% Define background TikZ picture
\newcommand{\BackgroundTikz}{%
  \begin{tikzpicture}[remember picture,overlay]
    \fill[blueA] (current page.south west) rectangle
        (current page.north east);
    \foreach \i in {1,...,500} {
      \pgfmathsetmacro{\x}{rnd*45}
      \pgfmathsetmacro{\y}{rnd*25}
      \node[white, text width=1.5cm] at (\x,\y) {♥};
    }
    \foreach \i in {1,...,500} {
      \pgfmathsetmacro{\x}{rnd*25}
      \pgfmathsetmacro{\y}{rnd*30}
      \node[blueB, text width=1.5cm] at (\x,\y) {♥};
    }
  \end{tikzpicture}
}


\AddToShipoutPictureBG*{\BackgroundTikz}
\begin{document}
\thispagestyle{empty}

% Your letter content
\begin{center}
  \Huge\color{crimson}{Hello dear world}
\end{center}

\textcolor{red}{%
  \textcolor{crimson}{\heartpar{\lipsum[1]}}
}

\end{document}