\documentclass{article}
\usepackage{subcaption,graphics}
\usepackage{color}
\newcommand{\rulesep}{\color{blue} \unskip\ \vrule\ } \begin{document}
\begin{figure*}[ht!]
\begin{subfigure}[t]{0.32\textwidth}
\includegraphics[width=\textwidth]{universe}
\end{subfigure}
\rulesep
\begin{subfigure}[t]{0.32\textwidth}
\includegraphics[width=\textwidth]{universe}
\end{subfigure}
\caption{set vertical dashed rule between image ?}
\end{figure*}
\end{document}
here the code of adding vertical rule. I changed the color, but I need to change also the style and thickness.


\newcommand{\rulesep}{\unskip{\color{blue}\ \vrule\ }}– egreg Dec 13 '17 at 07:17