Nikon D3100 Reds coming out neon?

I bought a Nikon D3100 DSLR back in April and I've been trying to get used to working it. I've been having this problem however and I can't figure out how to fix it. When I take a picture with anything black in it (such as my dark hair, or sometimes my daughter has her mouth slightly open) the black always comes out a neon red color. It's so difficult to fix and I can't figure out why it is happening! It's almost like noise, but why is it red? It's been happening for a while with many different f stop, shutter speed, and aperture settings. Any advice?

Yes. Since the camera is fairly new I have to assume you have warranty on it. Call Nikon and talk with them about it. It could be as simple as changing a setting but it may not be simple. In that case they may ask you to return it for repair. If that happens the repair should be free provided it's under warranty.

Actually "reds" are very hard for any digital camera to handle. They become over saturated when compared to the same shot using film.

If you are in the habit of shooting with your colour enhancement set to "vivid", you will want to neutralize the way the camera processes colours… Or shoot in RAW and take care of red over-saturation in post