If they are uniform and show a slight tint of the normal coral color (like super light pink on a red coral), then growth... usually. You should also just be able to tell that your corals are growing - take some photos to keep around for reference.
It takes a while for the zoox to populate the new growth areas, which is why a lot of new growth is a different colors... it is not always white and sometimes it is purple, green, etc. Some growth is the same color as the coral. This is highly variable.