I know policy questions aren't but I don't think this qualifies.

I was wondering why the thumbnails of some animated images, like web-m get blue borders but others like gifs, don't?

Because webms are a video format.

Maybe there should be a different colored border for each file type. :)

Blue borders are WebM while red border means the post got deleted, that's what i know about it.
Gifs i guess count as a picture like jpg/png's do, so they don't get a special border.

Why would anyone care if it was JPG/JPEG, PNG, or BMP?

We only need the border for GIF and WebM really

OK, so it's the format, not the fact that they are animated.

Got it. Thanks.

also keep in mind: not all GIFs are animated.
all WEBMs should be animated though (if you find any one-frame WEBMs go ahead and flag them)

Yup...and I have already made a ticket asking for animated GIFs to have their own border a couple weeks ago so it is on the agenda.