Thermochromic (color change with heat) PU faux leather material.  When heat is applied (or the surrounding environment is hot enough, ~75F), the black upper layer begins to vanish to reveal an amazing multi color print underneath. 

This material is also called "civilist" because something like it was used in the Nike SB Dunk x Civilist release.  This one is a bit different than retail, with a microfiber backing and a coating that makes it feel like actual leather.

~1.5 mm thickness, including the microfiber backing.

* WARNING - The integrity of the color changing effect is not permanent.   Over time the return to primary color (ie black) will diminish and the color may appear dull.  It should remain strong for a longer period of time if you do not leave it in direct heat (ie blazing hot sun) for hours at a time.