Blue is the light your plant reaches for, the tips of the leaves are sensitive to blue light and direct the plant to grow towards it by releasing chemicals as signals.
Plants use the length of night, not day to determine when to flower. A plant kept in a dark closet can be signaled to flower with just a short flash of red light. It is the red light seen as dusk the plants use as their flowering signal.
Plants use both blue and red light to feed themselves and slightly favor red.
Plants appear to be mostly green to us because they are reflecting the green light and do not absorb it so they can’t use it.