Color calibration pipette tool always makes it shift to red. It happens for the last few version, 4.6 at least. Any hints would be appreciated. Attaching sample image, it’s a white balance card on a black sheet, lit with a strobe light.
_DSC2182.NEF (26.6 MB)
People usually get this when they once use color calibration to colour-match images, taking a sample from a non-grey spot and setting it as the target. This is never reset automatically, not even if you reset the module or restart darktable.
Check that the target in the module has a saturation of 0.
See darktable user manual - color calibration
If you reset the L, h, c values, the default value is a neutral color at 50% lightness (middle-gray) – this can be useful to quickly set the average white balance of any image. If you want to match the control sample against neutral gray, you only need to reset the chroma slider because the lightness and hue settings have no effect on chromaticity for neutral grays.
Note that the target value is not reset when you reset the module itself, but is stored indefinitely in darktable’s configuration and will be available on next launch as well as for the next image you develop.
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That’s it! Thank you so much!
This is awful UX 
I think there’s now a warning in 5.0, so you don’t forget.
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I’m on 5.0 and there isn’t. Perhaps behind a setting…
Just adding a screen shot for clarity to help others who may read this post. I personally keep the area color mapping option expanded so I can straight away confirm the target is indeed set to grey and not another target value such as a skin tone. You can select a nice skin tone from another image and use it as the target for the current image which makes this module extra useful as often we don’t have grey cards but do have skin tones available in images.
BTW, what is the light source for this image? It seems strange and I was surprised that setting either WB module alone or color calibration module using the white card as a target produced a green rendition. Even using the grey card has produced off colors in my view for everything but the grey card itself. I presume this is an issue associated with the light source, but I am guessing here. Maybe a light source not covering the full spectrum?
Walls are green in that room 