Hello,
Sorry for the late reply (I just got back from the Dave Mathews concert at the Gorge
)
SPS corals and especially Acropora types often shift color from changes in lighting intensity and spectrum. The brand/type of bulb and the brand/type of ballast that drive it can dramatically change SPS colors. An example would be a 10,000K Ushio 400W mogul mount bulb driven by an HQI ballast. This combo will bring out a lot of purple, cream, and pink colors. Just change the blulb to a Reeflux 10,000K and many of the corals will turn blue and also appear more blue. Change the ballast to a standard magnetic one and the corals will darken and sometimes change color. The tank will also appear to have about 15% less light intensity and the bulb will burn a slightly different color.
With so many different bulb and ballast combinations out there you can only expect coral colors to remain about the same if you use the same lighting system they came from and place them about the same distance from the bulb.
Different brands of bulbs that are called 10,000K will produce very different peaks at certain wavelengths. Some have large spikes in the 420nm while others in the 450nm. These have a profound effect on color that we see and over time can change the actual color of the coral.
Be sure to realize that coral coloration is not an indicator of coral health, just the coral adapting to the current lighting conditions.
Regards,
Kevin