Answer: Red light
Explanation: Plants absorbed white light best than any other light, however, red light is better light than other lights after the white light due to its long wavelength and the right amount of energy to excite or stimulate the electrons of the light center of the chlorophyll and transit to a higher energy level which increases the rate of photosynthesis.
Red light is a light with a longer wavelength which helps in radiate and heat the chlorophyll than its counterpart. A high rate of photosynthesis results in more glucose production.