I thought to the fish atleast they could not tell the difference. I thought the blue light was just "our" choice. Meaning that the fish could not tell the difference between the blue (actinic) and the white(10k), to them its just light. Of course the more you add the brighter it gets to them(fish). I know its the "norm" for when you have metal halides to have the actinics come on first, mostly because they are not as powerfull as the metal halides. Therefore less shock to the fish. When you use several of the same wattage lights or close to it, it doesnt really matter what comes on first(to the fish atleast) The only reason you would stagger the on/off times is to build up and down from the full intensity of the lights. If that makes sense.
Of course I may be totally wrong on this...so someone will correct me Im sure.