Changing the color could have a negative or a positive impact. If the coral is not used to being blasted by high amounts of light it could bleach a little, but there is also a possibility that it could get better coloration. Like mentioned before, the amount of light is not the important thing when it comes to coloration. You can put a 400w 6.5k Iwasaki bulb and it will grow like crazy because they are super intense, but it will do hardly anything for the color. Gary gave us an example of a frag he gave to Texas Todd. Todd has an awesome lighting setup and he is using a combination of different bulbs, some of which include the reeflux bulbs. Reeflux bulbs peak at around 470nm and thats why it reflects nice colors of his corals. In addition, if I am not mistaken, Todd also has VHO actinic supplumentation that provides the 420nm that Gary was talking. 420nm not only reflects nicely of the corals but it also helps create the pigmentation in the zooxanthellae algaes. What type of 10k bulbs are you using?