The most reliable way to own the color version is through the official Human Centipede trilogy Blu-ray sets (released by companies like Shout! Factory or IFC Midnight). These sets often include the color version of the second film as a "special feature."
By removing color—specifically the red of blood and the brown of "other" fluids—the film was able to pass through certain international ratings boards that would have otherwise banned it outright for being "too realistic." The Appeal of the Color Version The Human Centipede 2 Color Version Download --BEST
He wanted the film to feel like a "dirty, vile" contrast to the clinical, bright look of the first film. The most reliable way to own the color