[Coral-List] Temporal colour change of coral from green to red

[Terry F. F. Ng]

Have anyone ever observed or recorded corals that can temporally change
their colour?

Recently I have been observing a green coral that can temporarily change to
red within a second. The extended tentacles are originally green in daytime,
making the colonies green. When the corals were touched, the tentacles
retracted and revealed the red outer layer, then the whole colonies appears
to be red. I guess there are some advantages associated with this colour
change: better protection with red colour when it is stimulated. Also, it
may be good to be green at daytime when the tentacles are extended, and be
red (or appeared to be dark) at night when the tentacles are retracted.

I am very curious whether other people have noticed this kind of coral.
Anyone might also contact me for further information.

Terry Ng
terryfeifan at gmail.com