Wear pulls in messages from any app that adds a notification to your phone, and sometimes that means a lot of text. To actually read more than a sentence or two, you basically have to touch the screen repeatedly.
Unfortunately, the screen automatically dims and goes back to black-and-white mode in about three seconds, and there’s no user-configurable option. This is a power saver on the Gear Live with its AMOLED display, but not so much on the G Watch. All you have is always on, or not always on. There really ought to be an option to set your own timeout.