I was going to suggest Paulette Goddard because I have one, but I perused my notes and can't find anything about when mine begins to bloom. It may be later than Christmas, but it is a good red. It is hardier than many others too.

There are a number of true reds, but based on your zone designation (7 to 8a), japonica blooms are scarce or even absent at Christmas time, unless we're having a particularly mild period. Temperatures below freezing keep flower buds dormant, and will turn open flowers to mush. Depending on the variety, japonicas in Atlanta open in late October to perhaps early December (Debutante is a good example), and then in February through March or so (most other varieties, such as Bob Hope or Royal Velvet - both deep reds).

I love Daikagura and it's blooming now. I went to the Clemson Botanical Gardens this past weekend where they have a gorgeous camellia garden. The Daik was the most true red that was blooming. Another that was blooming that is more cerise red (deep hot pink) that was very nice is Dazzler a sasanqua.
If you don't have any, I would plant some whites too. Winter's Water Lily is lovely and is blooming now.

Yuletide is popular but I don't care for it much.
I just bought a beautiful white j., at Lowes yesterday in full bloom that looks like a deep, huge white rose.(double peony I believe) I can't remember the name right now but it's out in the yard waiting for me to plant it. Hopefully it will bloom at this time of year next year!

Pansyface, have you considered going to Massee Lane Gardens? I think it is near your neck of the woods and the trip would help you see which varieties are blooming this time of the year. Plus you would also be able to tell how "deep red" their blooms really are. Luis