Neither! Or perhaps Darwinian. It is an idiosyncratic space all in our brains. It is our own learned synaptic weights and embeddings that allows each of us to effectively/efficiently use some of the data generated by our photoreceptors.

Sure, color space can be reformulated many other ways for applications but all just operational kludges.

It's non Riemannian and therefore also non Euclidean.

In Riemannian space, the distance between points is the length of the shortest path between them. Euclidean space is a subtype of Riemannian space, where angles in every triangle sum to 180°.

Both