Plants appear to be green because of light reflection. The molecules in the plant called chlorophyll absorb red and blue light from the colour spectrum but reflect green light, creating the green of plant stems and leaves visible to the human eye.
Kinds of Chlorophyll
Plants thrive by absorbing two kinds of chlorophyll from the sun. They gain their energy through light absorption from the red and blue parts of the chlorophyll. The remaining chlorophyll deters this absorption, and the resulting reflection makes the plants look green.
Other Functions of Chlorophyll
Besides giving plants colour, chlorophyll transforms sunlight into oxygen and carbohydrates through a process called photosynthesis. This provides plants with nutrients to survive as well as necessary nourishment to the animals that consume them.
Despite its spelling, chlorophyll has no relation to chlorine. In Greek, the word "chloros" means yellowish green, which also refers to the colour of chlorine gas.