Created attachment 573092 [details]
Not exactly sure how to reproduce this, but I have seen several times where the favicon gets to have a purple background if it has transparency. Attached is a screenshot that demonstrates it.
Note that the site actually has a favicon, it just didn't load this time, and it fell back to the default missing icon imagery, but with purple backdrop.
I think you are just seeing the temporary "color the favicon background based on SSL level"
I saw this with green backgrounds (github.com is an example). I also thought this was a bug but the SSL level makes sense, not sure it's particularly clear to users though.
could you verify that we no longer use colors here?
We use security lock (Bug 703115) and not colors anymore.
Fixed as a part of Bug 703115,
*** This bug has been marked as a duplicate of bug 703115 ***