The color itself isn't the thing really. It's what the color represents: all of the features that iMessage provides don't work with SMS. Instead of little icon

The color itself isn't the thing really. It's what the color represents: all of the features that iMessage provides don't work with SMS. Instead of little icon reactions, there are long messages ("pwinnski liked 'Okay, see you there'"), location-sharing is ugly, URL-previews are wonky, etc, etc. It's a diminished experience because SMS is a terrible protocol, the color just lets us know what to expect.