I've used https://pairdrop.net/ before to share files between devices on the same LAN. It obviously wouldn't have to be a website, but it's pretty convenient since all my devices I wanted to share files on already have a browser.
I interpreted this along the lines of it not being a pigment, rather it's black because something about it's physical structure at a small scale causes light to not reflect back. Adding a thin coating of gold would not necessarily change that structure so it would continue not reflecting light.