@Tobias I know this isn’t an official darktable support forum, they do not have one. being a member of the community, I just asked for help.
I downloaded from the link in this topic Color Manipulation with the Colour Checker LUT Module - #6 by patdavid
I’m on darktable 2.0.5 the latest
@Claes yes keep thing simple 
Thanks for your reply,
in lighttable I left click on a colourful raf to select it.
double clicked discard.
double clicked monochrome, the image does not turn monochrome.
in darkroom 1-orientation
2-sharpen
3-base curve- histogram changes
4- colour checker lut - Do not have this
5- tone curve- yes image gets lighter
6- input colour profile
7- base curve off - image gets duller.
input colour profiles same as both of yours.
Hope that helps 