My vote goes to U2’s Zooropa, which I happen to have as my desktop background. What others can anyone think of as being quite colorful? (And don’t say the Beatles’ White Album 
)
The Beatles- Sgt. Peppers Lonely Hearts Club Band
Santana “Abraxas” has a lot of stuff going on. And it has boobies. 
5000 Spirits or the Layers of the Onion by The Incredible String Band!
Axis: Bold as Love - The Jimi Hendrix Experience
Okay. How about Spinal Tap’s Smell the Glove?
Bjork’s Post is pretty garish.
What was the album from the 60s where the cover had a big wheel that you could spin behind the main cover and make little pictures on the cover change? I want to say either the Beatles or Led Zeppelin but I’m not sure. In any event, that’s the most colorful one I can recall.
BobLibDem: you’re thinking of Led Zeppelin III.
You are correct, gex gex , I found a picture after a quick Google. Thanks for the info, it brought back some memories.
I recently picked up the recent remaster of the Stones’ Their Satanic Majesties Request. It is definitely the most colorful, razzle-dazzle cover in my collection at the moment.