I wonder if RawTherapee could be used to achieve this effect. Perhaps buddingphotographer could advise on this.
RawTherapee is not really capable of that sort of editing, although if the one color you want to emphasize is distinct enough it might sort of work… If you’re already comfortable in GIMP, you can do a “selective color” edit much more effectively in GIMP/Affinity/Photoshop.