Ah, looks like it is the other way around (that is, edge browser is right) and it is indeed broken for all browsers. I looked up the generated code and it is the same for all browsers (more or less). The icon in question is:
http://www.whatsbestforum.com/images/statusicon/forum_new-48.png
I refreshed both IE and Edge browsers and they both show the blue icon. Here is the important bit: I refreshed Chrome and it too is displaying blue icons now! And as noted earlier by caliaripaolo, the favicon has reverted to vbulletin check mark instead of WBF. I seem to remember adding the "new" label to the ones I modified so I think they are OK but why they are blue now, is strange.
To replicate, just hit F5 in chrome and you should see all the icons on the home page become blue.
You need to go to the file manager and download the above icon and see what it looks like on your computer Steve. If it looks blue then the look of the forum style is reverted back and only the cached version in the browser remains for some users. The old styles need to be found and put back in (BTW, I tested all the styles and they all show the blue icons).
Or just open a ticket and cut and paste the above text and get URLJet to troubleshoot it.
The reason Chrome didn't get hit right away is that it is one persistent browser when it comes to caching. No matter how many directives you give it in the web page, it refuses to throw away the cached web content. It will however do it on its own at some time in the future so even if this is working for some, it will stop to behave that way. This made it hard in the past to test changes because it would continue to show the old even after I had made changes.