Jürgen Gebhart wrote:The color of the Hyla`s depents mostly on the temperature of the water and the air, some brown Hyla`s turn to green when they warm up. I don`t know if they do it all but most of them. Made this experience with Hyla arborea and Hyla sarda.
It's nice to see that in the early evening they start calling from land and once that they are calling out of the hoof prints from the cows in the mud at the edge of the pond they have those brown colour and when the go in to the water and start calling from the green vegetation the change in an hour too green.
The yellowgreen one on the picture was an old male at the end of his career.
Peter