Here’s a quick workflow to compress whatever version of Prototype you please.
Here’s something I worked on for a few hours just to amuse myself. I’d develop it further, but I can’t see how this has any sort of practical use (also note the caveats at the top of the script). So here it is: a web page desaturator. Takes all colors in linked stylesheets and turns them into grayscale versions. Here’s a demo using a page from the Prototype site. Firefox only.