[mfgs]

Cool. Interesting to note that the original is not necessarily the "correct" real world color palette (it's accuracy is subject to camera settings, sensor response, lighting, etc), so the colorized version could in theory be even better than the original in some or all areas of the photo.

[hilyen]

100% I think my original photo is a bit oversaturated. The real issues I see are where it makes blue things brown and red things green.

[npteljes]

As well as there are multiple desaturation methods, GIMP alone offers at least three, and I'm sure that could influence the outcome as well.

https://docs.gimp.org/2.8/en/gimp-tool-desaturate.html