Well blue or full spectrum white light is great for seedlings and vegetative growth, it primarily prevents stretching, and the reddish light is used for flowering, as it is what the plant mainly uses for energy. I only know about CFLs, so bacically for seedlings and vegetative just use the full spectrum or soft white lights which are considered to have more light in the blue spectrum. These lights will be somewhere around 5500k. Then for flowering use the reddish lights, they're usually 2700k or thereabouts. You can also just use the different spectrum lights together to get a good overall spectrum, at least when using CFLs.

Edit: and you can just get some regular clip on lights with reflectors.