When Apple launched the iPhone 7 back in 2016, it was available in quite a lot of colours as far it goes back then, nowadays the iPhone is offered in a wide variety of colours. The iPhone 7 was offered in Black, Silver, Gold, Rose Gold and Jet Black. The iPhone 7 was offered in PRODUCT(RED) six months after launching. The latter was a unique high gloss black which was a much deeper shade then the black and space grey colours Apple uses.
However it was prone to scratching quite easily and when it came around to the iPhone 8 and iPhone X in 2017, Apple dropped the Jet Black colour from the line up, but according to Mr. White on Twitter, Apple was testing a Jet Black iPhone X during the run up to the release of the device.
They have tried iPhone X Jet Black before pic.twitter.com/md5p9nNER3
— Mr·White (@laobaiTD) March 12, 2021
The prototype as seen in the image, doesn’t have an Apple logo or other markings which make it final, but it is interesting to see Apple was considering the colour.