I am following a tutorial and they start talking about it at this timestamp:
It seems like C4D's Field system exposes the color-remap information through a custom field that is then accessed by the external renderer. I have done a fair amount of development in UE4 (and am a web dev for work) so node based workflows are not new to me, but VFX is pretty new.
Is the codebase for CentiLeo all in C++ and then you have a build script with many build targets that builds it for a) each version of C4D and b) 3DSMax? I've also done a bit of GPU programming in the context of machine learning, but again, using GPUs for rendering is new.