Which colour of light is not absorbed by plants?

• A. Blue
• B. Red
• C. Yellow
• D. Green

Answer: (D)

Plants rely on light energy most efficiently from blue and red wavelengths because chlorophyll absorbs those colors to drive photosynthesis. The colour you actually see is what isn’t absorbed, so leaves appear green because green light is reflected rather than absorbed. In other words, green light passes back to your eye, while the energy from blue and red lights is captured to power the chemical reactions of photosynthesis. (Note that a little green can be absorbed by some pigments, but overall green is the least absorbed, making it the color not absorbed by plants.)