> Can it be formalized in standard terms from differential geometry? For example, than the color space has negative curvature? You're right that it can be form

> Can it be formalized in standard terms from differential geometry? For example, than the color space has negative curvature? You're right that it can be formalised in terms of curvature. But we can't say that it has negative curvature because the curvature is nonconstant. It in fact has positive curvature in some regions and negative in others.