Chlorophyll does not have only one molecule. There are various forms of chlorophyll that absorb the wavelength differently so that the process of photosynthesis is efficient enough for the plants or Algae. There is a green wavelength found in sunlight. While Algae and other plants absorb the sunlight from the sun they absorb all colors but due to the green wavelength present chlorophyll makes the plants and algae look green. Hence, Algae is green.