Chlorophyll makes plants and algae appear green because it reflects the green wavelengths found in sunlight, while absorbing all other colors.
However, chlorophyll is not actually a single molecule. There are 6 different chlorophylls that have been identified. The different forms (A, B, C, D, E and F), each reflect slightly different ranges of green wavelengths. Chlorophyll A is the primary molecule responsible for photosynthesis. That means that chlorophyll A is found in every single photosynthesizing organism, from land plants to algae and cyanobacteria. The additional chlorophyll forms are accessory pigments, and are associated with different groups of plants and algae and play a role in their taxonomic confusion. These other chlorophylls still absorb sunlight, and thus assist in photosynthesis. As accessory pigments, they transfer any energy that they absorb to the primary chlorophyll A instead of directly participating in the process. Chlorophyll B is mainly found in land plants, aquatic plants and green algae. In most of these organisms, the ratio of chlorophyll A to chlorophyll B is 3:1. Due to the presence of this molecule, some organizations will group the green algae into the Plant Kingdom. Chlorophyll C is found in red algae, brown algae, and dinoflagellates. This has lead to their classification under the Kingdom Chromista. Chlorophyll D is a minor pigment found in some red algae, while the rare Chlorophyll E has been found in yellow-green algae. Chlorophyll F was recently discovered in some cyanobacteria near Australia. Each of these accessory pigments will strongly absorb different wavelengths, so their presence makes photosynthesis more efficient.
