Selecting the optimal light environment for plant growth and development, and reducing the amount of electric energy consumed by lighting are both essential to improve the economic operations of vertical farming. Compared with photosynthetic photon flux density and light period, the effects of light quality on plant morphology and physiology are much more complex. The effect of light quality on plant growth and development has been a hot topic in vertical farming over the past few decades. In this chapter, the effects of monochromatic and polychromatic lights on growth, development and qualities of leafy greens are described. Different morphological and physiological responses to specific spectral stimulation are discussed, followed by common polychromatic spectrums and their effects on plants.