\begin{overpic}[width=0.49\textwidth]{tour6}
\put(1,74){\colorbox{white}{(\sublabel{tour6}) \href{http://dream.misasa.okayama-u.ac.jp/?q=20210114062012-906260}{tour6}}}
%%(\subref{tour6}) \href{tour6}
\color{red}
\end{overpic}