I love the Giesemann 13k/14.5k 250w bulb. I tried virtually everything there is in DE and it remains my overall favorite.
If your tank doesn't have micro algae issues, it will look bright white with just a touch of blue. The light takes on whatever the dominant color in your tank may be.....that's why you don't want lots of brown algae, hehe.
By the way, I've got a Giesemann 2x250w + 2x54w T5 brand new, never used, packed-up since day 1, sitting in my garage that is for sale. You can search for Giesemann in the "for sale" section of RC for details. It was shipped to me without ballasts and bulbs, but you can read the details for full disclosure.