The color of the item in the presentation was changed. But, In the table of content, I still saw old color and couldn't fine change the way of the color of the item in the table of content. I used the following setting:
\definecolor{subred}{HTML}{ff3333}
\definecolor{subsubred}{HTML}{ff6666}
\setbeamercolor{itemize item}{fg=red}
\setbeamercolor{itemize subitem}{fg=subred}
\setbeamercolor{itemize subsubitem}{fg=subsubred}
\setbeamercolor{itemize subitem in toc}{fg=subred}
\definecolor{myred}{HTML}{660000}
\usetheme{Copenhagen}
\useinnertheme{rectangles}
\usecolortheme{beaver}
\documentclass{...}
and ending with\end{document}
.