You should get those Philips Hue color lights that you can control with a computer. Since it's open source, you could actually control the lights with pretty much any internet connected device, including your vintage Macs.

So here's my idea: Take one of your B&W Macs and turn on the Text to Speech. Have it say something silly like, "See, I can do color, too!" and have it send a command to change the color of the light that's shining on it. )