Operating system: Linux-4.15.0-58-generic-x86_64-with-debian-buster-sid 64 Bits
Graphics card: GeForce GTX 1080 Ti/PCIe/SSE2 NVIDIA Corporation 4.5.0 NVIDIA 430.40
Broken: version: 2.81 (sub 8), branch: master, commit date: 2019-09-05 10:52, hash: rBb6e7e173ecd9
Short description of error
To desaturate a color you plug a HSV or RGB curves node. But the more you light up the color the more hue shifts. I've tested it with eyedropper in blender and gimp. Dragging the right side control of the RGB curves node (making darker) doesn't shift hue.
If i'm doing something wrong, then what's a correct way to desaturate a color without hue shifting?
Exact steps for others to reproduce the error
Open up the attached file
Fire the render
From the Picker node pick the color from the render view
Compare the hues on both nodes