\documentclass{article}
\usepackage{fontspec}
\setmainfont[Mapping=farsidigits,Script=Arabic]{XB Kayhan}
\usepackage{hhline}
\usepackage{colortbl}
\usepackage[RTLdocument]{bidi}
\begin{document}
این فقط یک آزمایش است
\begin{center}
\setlength\arrayrulewidth{5pt}
\setlength\doublerulesep{5pt}
 \renewcommand{\arraystretch}{2}
 \definecolor{orange}{cmyk}{0,0.61,0.87,0}
 \definecolor{indigo}{cmyk}{0.8,0.9,0,0}
 \definecolor{violet}{cmyk}{0.6,0.9,0,0}
 \newcommand\rainbowline[1]{%
 \hhline{%
   >{\arrayrulecolor   {red}\doublerulesepcolor[rgb]{.3,.3,1}}%
   |#1:=%
   >{\arrayrulecolor{orange}\doublerulesepcolor[rgb]{.4,.4,1}}%
   =%
   >{\arrayrulecolor{yellow}\doublerulesepcolor[rgb]{.5,.5,1}}%
   =%
   >{\arrayrulecolor {green}\doublerulesepcolor[rgb]{.6,.6,1}}%
   =%
   >{\arrayrulecolor  {blue}\doublerulesepcolor[rgb]{.7,.7,1}}%
  =%
   >{\arrayrulecolor{indigo}\doublerulesepcolor[rgb]{.8,.8,1}}%
   =%
   >{\arrayrulecolor{violet}\doublerulesepcolor[rgb]{.9,.9,1}}%
   =:#1|%
   }}
 \arrayrulecolor{red}
 \doublerulesepcolor[rgb]{.3,.3,1}
 \begin{tabular}{||*7{>{\columncolor[gray]{.9}}c}||}
 \rainbowline{t}%
 \arrayrulecolor{violet}\doublerulesepcolor[rgb]{.9,.9,1}
 وفا&خلیقی&یک&دانشجوی&ریاضی&است&
 \multicolumn{1}{>{\columncolor[gray]{.9}}c||}{حرف آخر}\\
 \rainbowline{}%
 1&2&3&4&5&6&
 \multicolumn{1}{>{\columncolor[gray]{.9}}c||}{7}\\
 \rainbowline{b}%
 \end{tabular}
 \end{center}
این صرفاً یک آزمایش است
\end{document}
