Seedling\Clone Scientific Question: can you be the one to answer it?

Which color, on the spectrum of light, will a seedling need to grow it's roots to prepare for transplant into a 50w HID HPS Hydroponics system with 18/6 lighting and spray n grow lightly misted with a tad of bushmaster and a pinch of moondust and a clone need that will need to grow it's roots to be transplanted into the same hydroponics system? (longest question in history I know...sativa is amazing, it's HD cannabis)

/bump
Anyone know? I wanna get little lights for my himd dome station