> When going LED they only use ones with the wavelengths the plants actually use. And those wavelengths are...everything except green. You can tell this becaus

> When going LED they only use ones with the wavelengths the plants actually use. And those wavelengths are...everything except green. You can tell this because plants are green, because they reflect green light and absorb everything else. So an LED-lit greenhouse looks "anti-green", which is some kind of reddish purple. It's a bit more complicated than this in practice, but not much.