New growth are the pink vertical and horizontal lines. There pink showing through the plastron as Yvonne mentioned is the torts insides. Because the plastron is flexible as a hatchling it sometimes can be transparent like in your case. The tort is constantly growing so is the plastron and carapce along with the bridge. I believe this is normal.
If I'm right in this when you see bright red spots under the plastron is time to panic as it's I believe internal bleeding? I think if yippy do a forum search you can find other examples of that.