The RED One’s sensor is natively close to daylight-balanced. While one can adjust it electronically to balance to tungsten, what that actually means is that the blue signal is being boosted to match red and green. This can lead to unwanted noise in the blue channel, which can be quite visible on the RED in the darker parts of the frame. The alternative is to instead put a blue filter on the lens to weaken the red and green channels to match the signal of the blue. It is essentially making tungsten light look like daylight to the camera.
Technically speaking, the absolute correct filter for this would be an 80B. This would get the native color temperature of the camera to about 34oo degrees Kelvin, or tungsten. But the problem with the 80B is that it blocks an enormous amount of light — about 1.5 stops worth. That makes for some pretty hard shooting on tight interiors with a bunch of hot tungsten lights all around. So a better solution is the 80D. This filter only eats about 1/3 of a stop and corrects the color close enough so that the modest boost of the blue channel still required does not raise any additional noise in the signal.