When there are unsaved changes, the save button is gray-blue. When there are no unsaved changes, it is gray. It is sometimes difficult to see the slight change in color of the little button. Could the saturation be increased on the blue button, or the darkness be decreased on the gray button to make the change more obvious? For example, if the gray button was less visible against the background, that would indicate it is not necessary to save.
What’s your use case for the save button? It doesn’t serve any real purpose beyond a throwback kind of reassurance to older word processor programs. SmartEdit Writer autosaves, and this can’t be switched off – the save button is really a “click it if you want to but you don’t have to” button.