This image was shot on a blue background and the red background variation was created in post.
Obviously, this needed a detailed mask around the fig & string of lights. Also, notice the cool cast reflected on the fig (boots, jacket, hair, etc.) that was neutralized and/or replaced with a red cast to look realistic.
Other shots in this shoot used similar techniques to swap scene colors, see featured images from the shoot featured here.
Need to make a major color swap while maintaining realism?