Starting with the main conversation screen, Google Messages appears to be going for a more desaturated look. The brighter color in the old UI is out, giving way to a dull background in the new UI ...

If something about Google Messages for Android looks different, it’s the tweaked design for the send button. This small change sees the send button in a conversation get bolder.

Google Messages now supports RCS self-messaging for high-resolution photos and videos. Messages sent to yourself aren't end-to-end encrypted though, unlike regular RCS messages.