Everybody has a question that why plants are green. The simple answer - that plants are green because they have green Chloroplasts (Cell organelles that carry out photosynthesis). And chloroplastids are green because they contain the green pigment chlorophyll in their thylakoid membranes, which is a pigment that absorbs red and blue light.
But why is chlorophyll green then? To understand why chlorophyll is green, we must learn about pigments. Do you know about Pigment? A pigment is something that absorbs light. Chlorophyll is a pigment that absorbs blue and red light. Chlorophyll is green because pigments absorb some wavelenghts of light and reflect others. A yellow pigment is one that absorbs all of the wavelengths of light except yellow. The yellow color is reflected into your eyes, and that is why it looks yellow. The reason a red shirt is red is because the red pigments in the shirt absorb all of the light except red. That reflected light is the color that the shirt appears. If it reflected all light, then it would be white. So plants are green because chlorophyll reflects green light. And chlorophyll is found in all plants because it is the molecule that absorbs the light that is used to make sugar.