GrowTutor

I have run HID's for years but just changed to a Lumigrow 650 LED. Always I used metal halide (blue) to generate vegetive growth and then switching to high pressure sodium (red) to begin and stimulate fruition.
With the unit I have purchased comes three light rheostats, red white and blue.
The question is, is there reason to combine red and blue at any time in a plants development cycle?
I suspect the white light is for observation purposes only.

Plants actually use quite a bit of the visible spectrum including green. During the veg cycle they still use red but depending on the plants and light cycle it can force them to flower earlier than desired. There are plenty of people that use HPS for veg *and* flower (because of the increased light output of HPS vs MH) but they often run 24 hours a day to prevent early flowering. With LED I'd use both red and blue for veg but I'd cut the red down if not running 24 hours a day. The white is also useful for the plants but most people use it for inspection. Again, if running 24 hours a day I'd turn them all up because more light is more light. Don't be fooled by the claim that a small LED is equal to a larger HID though; that claim is pure propaganda, based on the hundreds of LED grows I've seen, to justify the higher costs of LED.

YMMV...