Question: @ joanna why are corals different colours

Joanna Bagniewska answered on 20 Jun 2016:

The bodies of the corals, their skeletons so to say, are clear – but they are inhabited by tiny organisms called zooxanthellae algae. These are pigment cells with different colours; and they are so tiny, that several MILLION of them fit into a single square inch of coral. This means that different combinations of zooxanthellae algae would give the coral a different appearance. Also, these algae release colourful protein pigments in response to sunlight – and the coral’s colour depends on how much pigment is released and how much sunlight is available. In sunlight, humans get a sun tan – and corals become more colourful.