Okay, I'm being facetious in the title.
I knew at the outset that there was no reason for the server side processing, but I was avoiding the minor - but still of substance (e.g. an hour of my life) - creation of JavaScript code for the colour space conversions. I finally got a moment to hash that together tonight, so the page now allows for colour changes and variations entirely on the client side, with no post backs. I contemplated keeping the post-backs to have dubious functionality like "here's the colours that other users are creating!" but realized that would be pretty silly.
Visit yaflaColor today for all of your colour matching and scaling needs. I've tested with IE, Opera and Mozilla/Firefox, and it works successfully in those, but your mileage will vary (as it does depend upon DHTML and some less-standard elements of JavaScript). [UPDATE: After several updates more, I'm extremely satisfied with the results. Basically the only change that I still might do is improving the aesthetics of the sliders to rounded inlaid sliders, but otherwise it completely scratches my itch).
The tool actually served a really unintended, but valuable, purpose - My 2 1/2 year old daughter saw me testing it and asked to "play the color game". I hooked up a mouse and she was off and running, announcing the colour and then selecting it, celebrating on each new colour.