Most visitors to the reef comment that the coral isn't very colourful as they are used to seeing brightly coloured images in books and on television. Photographs and video are taken using lights to show the true colours of the reef. So the colours are there, it's just that you need white light to see them. This is why night diving on the reef is so spectacular. Coral are made up of a thin layer of living animals called polyps, which secrete a chalky, limestone skeleton as they grow.
Coral colonies grow as the polyps divide and multiply in a process known as budding.
Like all plants, zooxanthellae photosynthesize, producing nutrients from the suns energy which are used by the polyp for its own nutrition. Corals with zooxanthellae are able to lay down limestone skeletons up to three times fster than those corals without. Trying to identify particular species of coral is very difficult. What makes it so difficult is that one type of coral may appear as a branching form in calm water and look like a plate coral in another area. In many cases it is the environmental conditions, such as wave action, light levels and the amount of sediment in the water, that influence coral colony shape.