Does the tikz library `overlay-beamer-styles` support multiple fill colors?

Question

The following presentation depicts an empty circle emerging on frame 2. The color of the circle then proceeds to toggle between blue and red.

This presentation was produced with the following code.

\documentclass{beamer}

\usepackage{tikz}
\usetikzlibrary{overlay-beamer-styles}

\begin{document}

\begin{frame}{Frame \thepage}

  \[
    \begin{tikzpicture}

      \draw[
      , ultra thick
      , visible on=<{2,3,5}>
      , fill=blue
      , fill on=<{3,5}>
      ] circle (2cm);

      \draw[
      , ultra thick
      , visible on=<{4, 6}>
      , fill=red
      , fill on=<{4, 6}>
      ] circle (2cm);

    \end{tikzpicture}
  \]

\end{frame}

\end{document}

Here, the blue circles are defined separately from the red circles. I'm curious if it's possible to simplify this code by combining everything into one \draw command. I've tried doing

  \draw[
  , ultra thick
  , visible on=<{2-}>
  , fill=blue
  , fill on=<{3,5}>
  , fill=red
  , fill on=<{4, 6}>
  ] circle (2cm);

but this ignores all the blue circles:

Is there anything else I can do?

Answer 1

Yes, this is possible with the alt key (which derives from beamer's \alt command).

\documentclass{beamer}

\usepackage{tikz}
\usetikzlibrary{overlay-beamer-styles}

\begin{document}

\begin{frame}{Frame \thepage}

  \[
    \begin{tikzpicture}

      \draw[
      , ultra thick
      , visible on=<{2-6}>
      ,alt=<{3,5}>{fill=blue}{fill=red,fill on=<{4, 6}>}
      ] circle[radius=2cm];

    \end{tikzpicture}
  \]

\end{frame}

\end{document}

Answer 2

One way is use preaction and postaction options:

\documentclass{beamer}
\usepackage{tikz}
\usetikzlibrary{overlay-beamer-styles}

\begin{document}
\begin{frame}{Frame \thepage}

    \[
\begin{tikzpicture}[ultra thick]
  \draw[preaction={fill=blue, visible on=<{3,5}>},
        visible on=<2->,
        postaction={fill=red, visible on=<{4,6}>}
       ] circle (2cm);
\end{tikzpicture}
    \]
\end{frame}

\end{document}