This is the README for colourchange.sty.

Changes colour of beamer structural elements (e.g. the bars of outerthemes).
This is done either manually or automatically.

Don't use a colour theme or full theme (which sometimes call colour themes).
You should be OK calling inner themes and outer themes separately (although some look better than others at the moment: see bottom of readme).
You need to compile twice for it to work.

Requires packages etoolbox and calc.
Also needs some other stuff that is loaded by beamer.
Use with other classes at your own risk.

%------------------------------
% Summary of commands
%------------------------------

\selectcolourchanges{first}{second} takes two arguments: the starting colour and the final colour of the presentation.
These should be colours already understood by beamer.
Beamer uses xcolor, so you can define colours with xcolor commands and then use them in \selectcolourchanges.
That's what I do for the defaults.

\selectmanualcolour{colour}
Changes the structure colour.
Use between frames.
Can't guarantee this won't do weird stuff if you also have slidechange or framechange on.

Both commands also come with an american spelling version.
\selectcolorchanges and \selectmanualcolor are defined to be the same as the above two commands.
%------------------------------
% Summary of options
%------------------------------

defaultstyle
Turns on default inner and outerthemes.
Or rather, it will do soon.
That is, it turns on my favourite version of the theme, not the "beamer default" ones.
This is just a shortcut for:
\useoutertheme[footline=authorinstitutetitle]{miniframes}
\useinnertheme{rectangles}
Simple.

draft
The draft option turns off colour changing.
Good for speeding up compilation when drafting.

slidechange
Colour changes every slide.

framechange
Colour changes every frame.

%------------------------------
% To do list
%------------------------------

Make sure it works with all base inner/outer themes.
 - smoothbars, smoothtree do some shading-fu that breaks colourchange.sty's basic approach.
Check it doesn't hopelessly break article or handout modes
Make a .dtx

%------------------------------
% Other stuff
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Currently licensed under GPL v3. http://www.gnu.org/licenses/gpl-3.0.html

Original author and current maintainer: Seamus Bradley
tex@seamusbradley.net

Many thanks to the tex.stackexchange.com community for their help.
In particular, TH's answer to this question:
http://tex.stackexchange.com/q/7126/215

And Herbert's answer to this question:
http://tex.stackexchange.com/q/7427/215