Colorful Changing Shower Head
Even without batteries, it seems there would still be some kind of electricity generated within the shower head, which is a little weird to think about in the shower. There's also the issue of showering with the bathroom light off to get the full effect, but I believe if I leave the bedroom door a bit ajar I can find my way around. The shower head is on a wand-type neck. The product page says you can screw it directly into your shower pipe, but it looks like you'd have to remove any gooseneck to correct the angle, and you'd have to have a rather high shower pipe opening. But it would work perfectly screwed into a shower massage hose.
With a little more digging, I found a color changing shower that is not dependent on water temperature. In fact, the RIO Spectrum shower head lets you program the color changes ahead of time. The drawback is that it costs Â£2995.00. That's about $4,000! In contrast, the Colorful Changing Shower Head is only $17.73 from Budget Gadgets. That price goes down to $15.88 if you buy ten or more. Shipping is free.