My first thought was SEM image, but I would've guessed some kind of mineral, not metal. Makes me wonder what the false-color separation is based on, since it's my understanding that SEM images come back black and white. For instance:
https://timedotcom.files.wordpress.c...lity=85&w=1100
Meet the Ebola virus in what is probably the first SEM image to identify it. Most renditions of this image are false-colored, with the virus appearing yellowish on a light-purple background.
'Scanning electron microscopy' is a keyword string that can rabbit-hole an entire afternoon!