The "color" of light and its "temperature" are technical terms used to describe the quality of light. Black, emitting no light, is the base from which the color of light is measured in surface "color temperatures" recorded in degrees Kelvin (K). Lights with lower temperatures are "warmer" and redder. Lights with higher temperatures are "cooler" and bluer. A lit match has a warmer color temperature of 1,700K. Full summer daylight has a cooler color temperature of 6,000K. Plants are greatly affected by the color of light.
Growing plants thrive on blue light, 6,000K or higher. It is the kind of daylight you get in the spring and summer when plants are growing. You need blue light when you want the stalks and leaves of your plants to get larger and more robust. Seedlings and clones need blue light. Metal halide and some fluorescent lights give off high amounts of blue light. When the days become shorter, natural light gets cooler, turning orange or red.
Red light, 5,000K or lower, is best for plants that are blooming or yielding fruit.
High intensity sodium and some Light Emitting Diode growing lamps ordinarily give off lights in this range.
Some growers using greenhouses use artificial sources of red light to supplement natural blue light when their plants are yielding flowers or fruits. They use blue light to start their plants and get them off to a robust start and then use red light to finish them off.
Fluorescent grow lights ordinarily yield a light in the blue range, but some are marketed as full spectrum lights. This means they give off light in both red and blue range.
Infrared and ultra violet
We can see only a fraction of the light available from the sun. Only the light we can has any use for gardeners.
Infrared has a longer wavelength than that of red light. Most of the energy of the sun is infrared light. We can feel it as heat, but we can't see it.
Violet has the shortest wavelength that we can see. Ultraviolet is beyond that. Too much ultra violent can harm plants.