Change colors/contrast in beamer navigation between active and dimmed section

Question

The code below gives the following output for the head:

Here the first section on the left is active and the others not, but the difference is quite small, I would like the active section to be in gray. Is there a way to control how the colors are mixed, so that I can increase the contrast (by dimming the inactive section even further)?

\documentclass{beamer}
\usetheme{Singapore}
\setbeamercolor{section in head/foot}{fg=gray,bg=white} 

\begin{document}
 \section{one}
 \begin{frame}
 \end{frame}

 \section{two}
 \begin{frame}
 \end{frame}

 \section{three}
 \begin{frame}
 \end{frame}
\end{document}

Answer 1

You can use the apposite template section in head/foot shaded.

Example:

\documentclass{beamer}
\usetheme{Singapore}
\setbeamercolor{section in head/foot}{fg=gray,bg=white} 
\setbeamertemplate{section in head/foot shaded}[default][10]

\begin{document}
 \section{one}
 \begin{frame}
 text
 \end{frame}

 \section{two}
 \begin{frame}
 text
 \end{frame}

 \section{three}
 \begin{frame}
 text
 \end{frame}
\end{document}

With [10] it is defined the percentage of opaqueness.

Result: