It is true that is a good option.
But here is my 2 cents : As the icon works as a push button to obtain the save result, it is a button witch exists un two states (on/off, saved/dirty). So we could use the very same icon with different color AND orientation.
And visualy it convey an image of positive (tick up, like the commercials for watches set to 10:10 because it is like a happy face 
) versus negative (tick down like a sad face 
)