I just tried to look that one up, according to the net, rainbow rays is just a replacement bulb that has some logic built in but is extremely overpriced at over 300 bucks (if that's the one).
But, looking for this item led me to an LED place that sells MR16 replacement lights and instead of halogen they have LED technology in them, since halogens run on 12V DC and these LED lights do as well, I don't see a problem installing one of these in a waterproof housing - according to the site:
"They are highly suited to waterproof situations as the LED's sit inside the rim of the bulb."
So, when my Aqualuminator bulb bites the dust, I will be retrofitting the light head with a whopping 16 dollar MR16 automatic color changing LED.