Is Sketchfab working on 3M support? It seems like good and open format to share more meta data with files, like color.
http://3mf.io/
https://ultimaker.com/en/blog/19868-an-introduction-to-the-3mf-file-format
https://ultimaker.com/en/blog/22463-the-evolution-of-the-3mf-file-format