One is black-and-white and the other isn’t. They can be quite different.
For me, using Internet Explorer, the tab for the profile of a user
with an emoji in their name shows the black-and-white form,
and so should the tab for this thread.
I don’t like the color form of the cat emoji, so I’ll probably stop using it soon.
Apple, Google, Microsoft, Samsung, LG, HTC, Facebook, Messenger, Twitter,
Mozilla, EmojiOne, and emojidex [not a typo] each have their own forms for
all emojis. Whatever the Coffee Room runs on uses the Twitter forms.
Those are all in addition to the black-and-white (basic?) version.