Something to add that I didnt see touched on here is that visible light color is not the same as actual wavelength color.
Visible light is viewable to the naked eye in wavelengths of about ~400nm to about 700nm.
As you may recall from elementary school, you can blend two colors together to make a completely different color.
For example, if you were to mix the color Blue (~475nm) with the color Yellow (~570nm) you would not actually see the color green (~510nm). You would actually be seeing both the 475nm and 570nm wavelengths at the same time.
That does not mean that your eye would be experiencing the green 510nm wavelength. That's simply the way your brain would interpret the two colors your eye was actually receiving.
This is important because many different companies use various LEDs that offer colors that may not be nanometer specific. Photosynthesis is highly dependent on receiving the correct spectrum of light in order to make the process happen.
Another thing to consider is that all light is radiation. Radiation can be dangerous to living organisms. Ultra Violet Radiation (UV) is able to penetrate the DNA and break it up. This causes cellular mutation (Cancer) and can kill the organisms affected by the radiation.
Coral produce pigments to protect themselves from harmful radiation much like we do. When a fair skinned person is out in the sun for a period of time their skin begins to turn red and burn. Naturally their skin begins to produce pigments to protect themselves from this radiation and that person begins to tan. When a coral is exposed to harmful radiation it begins to "tan"... the colors intensify and become more predominant than previously.
This is great, we love to see bright vibrant corals in our tanks! However, if we push the limits of or corals ability to protect themselves they will ultimately perish.
I think LEDs are the future of reef lighting. However, I think we will see much advancement in the next 5 years or so. In my opinion, UV LED bulbs should only be used on controllable/dimmable units. I think fixtures in the future will have control over white/blue/UV so you can fine tune the appearance of your tank and not burn out your coral.
All this being said, Lighting is a very important part of our reef aquariums. It is just as important as salinity, ph, alk, or any of the other environmental variables we are concerned with in our tanks. We should always proceed with caution when changing the variables in our systems, and not be afraid to change things back if necessary for the life of our inhabitants.
If you are going to make a change to your already successful system, do it wisely and do as much research as possible before the change. If you are going to do something as drastic as changing from metal halide or t5ho lighting to LED, prepare to keep your existing lighting until you are sure the new lights will be sufficient.
Happy Reefing...

rder