You may notice a slight difference in your corals until they adjust to the new lights, but it should not kill anything or cause any serious harm. They should adjust to the new lights within a few days. As far as color goes, it is completely personal preference. I really prefer the blue hue that 20,000 K produces and the increased coloration of corals under it, but it is your tank and your choice. 10,000 K is supposed to be crisp white, but to me it looks slightly yellowish and pales in comparison to the coloration of corals under 20,000 K.
:joy: