Making an AVO fader LOL

I had an odd request, which I could not seem to get to work. The user, an obvious avohead, wanted a fader, for the colorwheel on a cyberlight. I tried everything (I could think of) -- IPCB, man xfade, etc, and no success. Any ideas how to do something similar to this? It's come up more than once with something like color, gobo, anything thats not 0/255ish.
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