# Beamer overlay with columns - changing image and highlighting text

I am making a presentation to explain an algorithm which produces a picture. I want to use two columns to have the picture on one side and the algorithm on the other. I want to click through the algorithm highlighting successive steps in bold or a different colour and have the image change to show the relevant step as I go. So far I have tried this:

\begin{frame}
\begin{columns}
\begin{column}{.5\linewidth}
\includegraphics<1>[width=\linewidth]{step1.pdf}
\includegraphics<2>[width=\linewidth]{step2+3.pdf}
\includegraphics<3>[width=\linewidth]{step4.pdf}
\includegraphics<4>[width=\linewidth]{step5.pdf}
\includegraphics<5>[width=\linewidth]{step6.pdf}
\includegraphics<6>[width=\linewidth]{step7.pdf}
\includegraphics<7>[width=\linewidth]{result.pdf}
\end{column}

\begin{column}{.5\linewidth}
\begin{itemize}
\item \only<2>{\color{blue}} Split into 8 sub-cubes (generation 1)
\item \only<2>{\color{blue}} Select fertile sub-cubes
\item \only<3>{\color{blue}} Split fertile sub-cubes (generation 2)
\item \only<4-6>{\color{blue}} Repeat until maximum generation  reached
\item \only<7>{\color{blue}} Place stars
\end{itemize}
\end{column}
\end{columns}
\end{frame}


But that seems to make all the \items blue until I reach that step, then turn them black. I want them all to be black except the one I am highlighting.

One option using the alert@ specification for overlays to highlight text on desired slides; for example,

\item<3-|alert@3>


shows the item text from the third slide on and highlights it on the third slide only. The color used to highlight the text can be changed using

\setbeamercolor{alerted text}{fg=<color>}


The code:

\documentclass{beamer}

\begin{document}

\begin{frame}
\begin{columns}
\begin{column}{.5\linewidth}
\includegraphics<1>[width=\linewidth]{example-image}
\includegraphics<2>[width=\linewidth]{example-image-a}
\includegraphics<3>[width=\linewidth]{example-image-b}
\includegraphics<4>[width=\linewidth]{example-image-c}
\includegraphics<5>[width=\linewidth]{example-image-16x9}
\includegraphics<6>[width=\linewidth]{example-image-16x10}
\includegraphics<7>[width=\linewidth]{example-image-golden}
\end{column}

\begin{column}{.5\linewidth}
\begin{itemize}
\item<2-|alert@2> Split into 8 sub-cubes (generation 1)