According to the Oregon State University (OSU) Extension Service, blue light from the visible spectrum is a critical quality of light for promoting vegetative, leafy growth in plants.
The OSU Extension Service also says red light from the visible spectrum is an ideal quality of light for encouraging flowering and budding.
White light includes all colors of light in the visible spectrum. Sunlight and the light produced by certain light bulbs emit white light, which is ideal for promoting growth in all stages of a plant's development.
Light intensity is an important factor in plant growth. Lumens measure light intensity; generally the more lumens a plant receives, the greater the potential for growth in every stage of a plant's development. But all plants need some level of darkness so they can respirate, according to Gardener's Supply Company.
ACF Greenhouses says gardeners who grow plants indoors should utilize certain light bulbs like metal halide and fluorescent because they emit bluish-white light. High-pressure sodium bulbs are often used to promote flowering because they emit a reddish-orange light.