Plants are green because of a pigment called chlorophyll. This pigment is essential for photosynthesis, the process by which plants convert light energy into chemical energy.

Here's how it works:

* Chlorophyll absorbs light energy: Chlorophyll absorbs light from the sun, primarily in the red and blue wavelengths.

* Green light is reflected: However, chlorophyll doesn't absorb green light very well. Instead, it reflects it back, which is why we see plants as green.

* Energy for photosynthesis: The absorbed red and blue light are used to power the chemical reactions of photosynthesis. This process creates sugars that provide energy for the plant to grow and thrive.

So, green plants are essentially reflecting the light they don't need for photosynthesis. This is a highly efficient strategy that has allowed plants to thrive on Earth for millions of years!