SteamOS 3.5.5 has been released to the Stable channel for Deck with the following changes: Display The default color rendering for Steam Deck LCD 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. The settings can be tuned with a preview of a test image (above), or with your running game.

tl;dr Steam OS 3.5 released to stable branch, adding sRGB emulation, and HDR and VRR (for external devices)