if you can get yer hands on a copy of natural reef aquariums they have a nice photo spread of the same reef under different lights, everything from 6500 to 20000k, and yes, in all of the tanks i have seen with 20k the water is definately more blue than white. i wouldnt call it as blue as pure actinic however... but definately not a pure white.
also you can do a ton of searches online... any tank you see that does not have a daylight vho supplement for 20000k will be a closer replica of a deep reef community than a standard sps reef community.
there are dozens and dozens of peoples tank pics in the photo section, you can look at those and see what different bulbs look like.
as for growth, the guy who runs the sps prop business near my house said he tested his bulbs, and from the viewpoint of a salesman, whose income is based on growth, i am going to believe him when he says his very careful tests show significantly more growth under 6500k than anything higher.
he has been doing it for many many years... and is quite sucessful.
here is his tank with 6500k and vho actinic supplement:
