RE. Re. Re. trolls
I tried to post some notes on comparative physiology to Wikipedia but it was summarily deleted for being "Original Research"
Essentially the Gliese 581d inhabitants are 3 1/2 feet tall, grey and due to the low light conditions and primarily infrared spectra of the star have large eyes with internal lenses to focus the longer light.
The skin colouration is due to having to absorb energy for metabolism, much as Earth type reptiles do and this makes them highly dependent on temperature for survival.
As far as communication, the skin is biomimetic much as chameleons are and can indeed change colour and shade VERY quickly which explains a lot of the inconsistencies in witness reports.
They are able to communicate using this ability and exchange information as skin patterns which allows for massively increased transfer efficiency over speech.
I have theorized that at the time of the Wow! signal Gliese was in the right position for Jupiter's magnetosphere to act as a deflector and focus enough signal to Earth to be detected.
This is consistent with observation and as the signal was only focused on the Solar System for a very brief time due to the massive power requirements it was not repeated.