Oh, colour change, that's pretty easy. :p I thought you meant you needed the slideshow to start during the loading time. xD
Give me a few minutes; I'll have something then. :p
EDIT:
Here's the function. This goes in the <head> of the document, because that is the first to be processed by the browser, and we want it to change colour during the loading time:
<script type="text/javascript">
function omghi()
{
alert('Now changing colour');
document.bgColor='red';
}
</script>
That says "when you call the function omghi(), alert the user, then change the colour of the background to red.
Next, we need to call the function. We want it to trigger automatically, so we have to use the :bou::bou::bou::bou::bou::bou: event, which calls a function when the page loads. The :bou::bou::bou::bou::bou::bou: event should be placed inside the <body> tag, because this is what is displayed on the page, and thus, the content whose loading time we are using:
<body :bou::bou::bou::bou::bou::bou:="omghi()">
Then all we need to do is combine them into a page:
<html>
<head>
<title>Hello</title>
</head>
<body :bou::bou::bou::bou::bou::bou:="omghi()">
</body>
</html>
And there you have it. :p