You can change the brightness in witcher senses ("cat potion" effect). Mod has independent settings for brightness:
1. In a dark place only
2. Outside a dark place during the Night
3. Outside a dark place during the Day

You can change the tint of the surrounding world. If you set all "RGB" settings on "255", you get full "decolorization" effect, but highlighted objects will remain colored. (It's my favourite set, highlighted objects is very visible)

You can change the fog density, if you want good visibility in a foggy weather.

Manual installation:
1. Copy "bin" folder in main game directory and confirm folder merge
2. Copy "mods" folder in main game directory and confirm folder merge
3. Copy "DLC" folder in main game directory and confirm folder merge
4. Use "Script Merger" for merge "Immersive Witcher Senses" mod with other mods
5. Open folder "Input", and open "input.settings.txt" in "Notepad", copy all strings
6. Open folder "C:\Users\*your user name*\Documents\The Witcher 3", and open "input.settings", paste all strings at the very end of the file
7. Open folder "Input" again, and open "input.txt (not input.settings.txt)" in "Notepad", copy all strings
8. Open "*main game directory folder*\bin\config\r4game\user_config_matrix\pc", and open "input.xml", paste all strings after "<VisibleVars>", at your discretion, but before "</VisibleVars>"
9. Start game, go in "OPTIONS\MODS\IMMERSIVE WITCHER SENSES" and customize mod, go in "OPTIONS\KEY BINDINGS", find "Desaturation In Witcher Senses Toggle Button" and change to another button, if you want
10. In the game press "F9" or another button if you changed it, for enable/disable Immersive Witcher Senses