Since yesterday there have been a few new visual icons in Office 365.
New Documents are now marked with 3 fingers? Or maybe it’s a bright spark.
Note that the icons come in different colours. The colour of the new icon matches the main colour of the site. So if you use the out of the box site icon this will match the colour of the new icon:
I also tested this on modern lists, but new list items aren’t marked. Not sure if this is an oversight or just a planned feature.
Slightly less easy to notice is the Share option on a single document when you hover over the document:
the same Sharing option can also be found in the modern lists: