I am successfully growing it without CO2. I feel like that is a feat within itself. I can get it red, but not even a vibrant red. This tank has some vibrant deep reds btw.
I think it will be impossible to have anything but a duller red without high light, which will require CO2 as well. Not a good choice for low tech, I feel like I have almost mastered the non-co2 low tech in terms of color and it's not the best plant choice.