The Wii U only supports limited RGB (16 - 235 range per color channel). Any sane HD console, like Xbox 360, PlayStation 3, and Switch allows the video output to be configured to full RGB (0 - 255 range per color channel). Graphics are rendered internally by the video card will full dynamic range, so video output is forcedly constrained by then mapping to the smaller dynamic range (historical broadcast range), to accommodate low quality/old TVs. Most TVs support both RGB mappings, so there's no reason to throw away the extra range by not providing a configuration option (Nintendo's infinite wisdom). Has anyone tried hacking the video device to enable full RGB output? Is a complete IOSU hack still required before this would be possible?