Ol Bob Millers bottling had made a red "sasparilla." But I believe they went out of business a year ago.
http://www.popsoda.com/olbobmilreds.html
I have a list of over 1800 sodas made within the US. Of course it's not with me, but I'm pretty sure there were a couple other red Sarsaparillas on it.
I know Anthony had tried at least the Old Mill brand, it's red. He didn't care for it if I remember.
Hosmer Mountain had a sarsaparilla, I think it had caffiene, but it's not on their site anymore.