10,000K = white light, 15,000K= light blue and 20,000 K=blue
Coral grow faster with 6500K or 10,000 K but most people don't like the look of the washed out color of just the 10,000K. They usually add antinics to add more blue and florescence.
The bluer the color the slower the growth usually. Chose the color that works for you.
david