SteamOS 3.5 has just been released to the Preview channel, and includes new features that are still being tested. You can opt into this in Settings > System > System Update Channel. Display The default color rendering for Steam Deck has been adjusted to emulate the sRGB color gamut, resulting in a slightly warmer and more vibrant color appearance. Added Settings -> Adjust Display Colors, to tune the display's Color Vibrancy and Color Temperature.
That seems like something a third party company like 8bitdo or Gulikit would have business creating, and they likely wouldn’t do a bad job.