In theory, plants are green because the leaves mostly reflect the green part of the spectrum. New insights show that only 10-15% is reflected, leaving 85-90% absorbed and transmitted through the leaves. Where blue and red light only penetrates the upper leaves, 10% of green lights is also transmitted to lower leaves for photosynthesis. Absorbed by pigments such as phycoerythrin, penetration and absorption in leave tissue is deeper and drives photosynthesis. Although green light is less energy efficient than blue and red light and on paper negatively influences PAR photon yield and efficacy, it is necessary for the plant's health and optimum development.