They happen on the screen as well, but the screen profile can be different to the output profile. For simplification I refered to output profile.
This solves the question 
Thanks, I see it is all about re-mapping the RGB coordinates in different color spaces.
1 Like
Exactly! 
@heckflosse, I forgot to point out that part of my confusion came from the behaviour of the lockable color picker: it allegedly works using the rendered histogram which, in turn, is influenced by a button you mentioned earlier:
“If enabled, the working profile is used for rendering the main histogram and the navigator panel, otherwise the gamma-corrected output profile is used.”
I feel the pieces of the puzzle fall into place now.
Hopefully this helps other folks too !
1 Like
We should describe this better in Rawpedia and also in the tooltip. The tooltip doesnt mention the color pickers atm. That’s indeed confusing.
@heckflosse what changes do you propose to RawPedia?
I can not find the scene (screenshot) you posted on my darktable interface. Could you help?
darktable ?
Oh!!!Sorry : )) I need more sleep.
1 Like
This is a common occurrence for me. FLOSS stew past bedtime. 
sRGB, Rec709 etc. are not constant luminance colour spaces (i.e. some of the luma information is carried in the chroma signal and vice versa). So you’d expect changing one channel to affect the others.
More recent colour formats like Rec2020, ICtCp, JzAzBz have much better separation.