Excellent! I think the colour is right where it should be.
Regarding Ha, this object doesn't really give any Ha signal. For some reason that I'm not aware of, there are no prominent HII regions in NGC 3718. I've never seen a photo of NGC 3718 with visible HII regions. This is a bit surprising - the close encounter with NGC 3729 should initiate a lot of star formation, and certainly there is plenty of young star clusters. So why don't we see any HII regions? That said, it could add a bit to NGC 3729, but probably not much. For other interacting galaxies, e.g. the cocoon galaxy, a Ha exposure is definitely adding a lot to an image.