At the aquarium we were shown blue light shining onto the coral.
Apparently this coral obtains most of its energy by having a symbiosis with a unicellular organism which does photosynthesis, hence the need for light. I asked about why blue light. I was told that the photosynthesis would work in white light but that the blue light is used so that the green colour is very clear. There was ambient white light from the room as well that gets in through the front of the tank. Perhaps it is the reflection of part of this that I was seeing in the green colour because in colour theory, surely shining blue onto green should look black. Or else the blue covered a vast slab of wavelengths that included green.
