Two issue could be at play here. One of those is already dealt with by Len Philot and the Eek… link he posted.
The other issue is a basic native colour profile for the 90D. Out of the box the colours are way off due to a lack of an automatically applied profile for this camera type.
You haven’t answered which RawTherapee version you are using, so point 2 needs to be answered for 2 situations:
-
You are using an old version of RawTherapee (this one].
First of all: get a recent development version as mentioned in my previous post. But, this version can be used if need be.
This version does not come with a native Canon 90D DCP profile. This means that you need to download and safe the profile that was provided in post #5.
Now start RawTherapee, load a canon d90 cr3 image, got to the Colour tab, then Colour Management. Select Custom, browse to the location that you saved the DCP file to and select it.
Tada! Correct colours are back. -
You are using a recent RawTherapee version.
As mentioned by Roel, this one natively has this profile. It isn’t yet picked up automatically due to lack of cr3 exif support, though.
You do not have to download the DCP file as described above in point 1, the other steps are roughly the same: When you select Custom and start the browsing process you are initially send to the directory that holds the native profiles. Look for Canon 90D and select it.
For the moment all this is an action that needs to be done by hand every time you load a 90D image. If you want/need to automate this go and have a look at these 2 RawPedia articles:
EDIT: Spelling and some clarification.