To your question about WMR: no similar setting that I know of but it has been requested and you can vote too:
Provide a Sharpen strength setting, and more post-processing effect controls in VR
However about the SteamVR settings you got me puzzled:
hmdDisplayColorGain# as well as analogGain are SteamVR settings only affecting Index headsets and are not affecting therefore any other headset (G1, G2, etc…). These have nothing to do with the application you’re using it with either, they are just SteamVR settings for Valve headsets, and this works directly at the LCD panel level.
However there is OVR Toolkit offering RGB adjustments to other headsets but it is not at the LCD panel level. Instead, it is overlaying the display with a tinted transparent layer which is changing the color but also altering the luminosity and the dynamic range, because it is modifying pixels values in the sRGB domain and in 8 bits resolution.
It is possible OVR Toolkit is “re-using” the same SteamVR json values for its own use but I doubt it.