I want to change the border color of the mdframe box. By default it take black.
\documentclass{article}
\usepackage{xcolor}
\usepackage{mdframed}
\newtheorem{mdtheorem}{Theorem}
\newenvironment{theorem}%
{\begin{mdframed}[backgroundcolor=lightgray]\begin{mdtheorem}}%
{\end{mdtheorem}\end{mdframed}}
\begin{document}
\begin{theorem}
Sample
\end{theorem}
\end{document}
My Default output is,

My Expected output is,

Any one suggest me the correct. I am new to LaTeX.
