Photosynthesis is an important process in plants in which they produce glucose which serves them as food. This process occurs in the green leaves of the plants, thanks to the green pigment chlorophyll in the organelles known as chloroplasts.
If the question is what will happen to the plant, it will no longer have green leaves, and the rate of photosynthesis will be significantly decreased, but not stopped because there will probably be other pigments (non-green) able to absorb sunlight.
If the question is what will happen to chloroplast if it is taken out of the cell and illuminated, its pigment chlorophyll will absorb red and blue light,and reflects green light.