Feature request: Per-monitor color controls (saturation, gamma, color temperature, etc.)

[NamTranVN2719]

Motivation

Many laptop displays have poor color reproduction and look washed out.

On Windows, I usually increase the saturation by around +75% using Intel Graphics Command Center, which makes the display much more vibrant and comfortable to use.

On Wayland, there is currently no compositor-level way to achieve a similar effect in Niri without relying on external workarounds or gamescope for individual applications.

Proposal

Provide compositor-level color controls, preferably on a per-monitor basis, such as:

• Saturation / Vibrance
• Color temperature
• Gamma
• Contrast
• Brightness (software adjustment)
• Optional: color profiles or other color adjustment APIs

An IPC interface would also be very useful so desktop shells (such as Noctalia) or third-party utilities could expose sliders without Niri needing to implement its own settings UI.

Benefits

• Better experience for users with washed-out laptop panels.
• Consistent color adjustments across all applications.
• Per-monitor customization for multi-monitor setups.
• Removes the need for external tools or game-specific workarounds.