I don't think it really matters. The example I gave uses a 20w fluoro, probably in the 6500K range. There are more cloning examples in the first link in my sig. One guy just puts them on the window sill out of direct sunlight or 7 ft. away from a 100w incandescent while rooting. Don't worry about the light as much as getting them to root. Too much light will make it harder to root.