I have made the following table:
\usepackage{tabu}
\usepackage{xcolor,colortbl}
\begin{center}
{\tabulinesep=1.2mm
\begin{tabu} to 0.9\linewidth { |[2pt] *{3}{X[1 c]|}[2pt] }
\tabucline[2pt]{-}
\cellcolor{green!20}\textbf{Parameter} & \cellcolor{green!20}\textbf{Value} & \cellcolor{green!20}\textbf{Units} \\ \tabucline[1.5pt]{-}
\multicolumn{3}{ |[2pt]c|[2pt] }{\cellcolor{green!20}Nose Parameters} \\ \tabucline[2pt]{-}
$\alpha$ & 10 & Deg \\ \tabucline[2pt]{-}
\multicolumn{3}{ |[2pt]c|[2pt] }{\cellcolor{green!20}Body Parameters} \\ \tabucline[2pt]{-}
$d_{B}$ & 122 & mm \\ \hline
$L_{B}$ & 2670 & mm \\ \tabucline[2pt]{-}
\end{tabu}}
\end{center}
However the title cells arent get affected by \cellcolor.
I have tried to update the package as I read it might effect but it did not work.
Thank you.

