\documentclass{book}
\usepackage{color}
\usepackage{xepersian}

\makeatletter
\definecolor{bl}{rgb}{0,0.2,0.6}
\let\LaTeX@startsection\@startsection
\renewcommand{\@startsection}[6]{\LaTeX@startsection%
{#1}{#2}{#3}{#4}{#5}{\color{bl}\raggedleft #6}}
\makeatother

\settextfont{Tahoma}
\begin{document}
\chapter{حد}
\section{حد راست}
متن 
\subsection{حد چپ}
متن
\end{document}