Hello everyone,
Are the colours right?
Yep. You nailed it!
The white paper and the coin on the picture are both helpful to “white balance” this image 
If I don’t photograph professionally, I do so only from the “artistic” aspect, the accuracy of the reproduction plays hardly any role for me.
As for myself, I take pictures mostly for work, as a plant pathologist.
I consider this both a bliss and a curse.
A bliss because I always strive to take the most accurate picture out of my samples (low ISO, no strong shadows, no diffraction etc). By doing so, in post production I limit myself to some little cropping and a bit of sharpening. Most of all, I never change the colours of my samples in the pictures (they must be accurate as regards the subject displayed).
A curse because I have never learned properly how to work with RawTherapee since my pictures have usually little noise to correct, no strong shadows to decrease and so on. As a consequence, I am not forced to learn this software and I am still a beginner as regards its tools…