How to distinguish a GoPro hero 4 black from a GoPro hero 4 silver or any other GoPro models?

How to distinguish a GoPro hero 4 black from a GoPro hero 4 silver or any other GoPro models?
Added (1). The reason i'm asking is because i intend on purchasing a gopro hero 4 from craigslist and in all honesty, all gopros look the same to me. Is there any aesthetic differences that might help me distinguish the gopros? If not aesthetic, then maybe software or whatnot?

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