The red milli might be the same acro as the one I circled, just fragged from the same colony and on a different plug. It has it's polyps pulled in so it might have the same green polyps. This is a milli I have called a MattV Red Dana and it's hard to tell it is red:
When the polyps are fully out, you can only really see the green encrusting base.
You can also see in that shot my shortcake. They are beautiful corals, just need more flow and light. The flow would be the hardest to do in a 5g, you mentioned you have a good light. Blasting flow through a smaller tank is difficult to dial in and not overflow, blow sand everywhere or not suck up small fish friends.