Win Explorer File Preview muted (until file is edited)

All,

Strange problem that happened about a week ago, which is file previews in WIn Explorer are muted, however will turn their normal vibrant color once edited. The example only shows image files, however this is the same for Word docs, System files, etc. (doesn't matter the file type).

I don't remember a Win update at the time, and can't remember flipping a switch anywhere that would have caused this, and in working with Windows since the early 90's I've never seen this.

If anyone has come across this and knows a fix, please let me know. It's not disrupting workflow but is is slightly annoying.

Thanks!