Fun fact: The frogs also can change color from black to green and back (perhaps dark green to light green).

They have some cells in the skin with black blobs full of melanin, and they can move them. Usually they are disperse and the color is dark, but with some hormone the blobs are transported to the nuclei of the cell and the color is light.

We used cells of this frog in a undergaduate lab for physics. The main task was to fine tune a microscope to track the blobs. So we cultivate the cells for a week (from a cell line, the original frog was gone long ago), we put the cells under the microscope and add an hormone to force the change of color in a minute or so. (I think in the wild the change of color is very slow.)

Something like this (not my video): https://www.youtube.com/watch?v=vqJSA_v0ics