How do you justify the idea she'd be worse at picking colors that go together?
If you pick points that are close together in four-dimensional space (to make a simplistic analogy) they'll continue to be "close" in a topological sense under any linear projection to three-dimensional space. Or for a different analogy, if objects group together under a filtration, they'll continue to group together under a coarsening of that filtration.
"Go well together" is different than "close together" if we are talking about matching clothes. Color matching effects is based on distances in the color wheel. Closest together is boring, largest distance is jarring. If you imaging a new axis only visible to tetrachomats, the color matching effects appreciated to a tetrachomat will most likely not have the same effect or even be visible to regulars.
If you pick points that are close together in four-dimensional space (to make a simplistic analogy) they'll continue to be "close" in a topological sense under any linear projection to three-dimensional space. Or for a different analogy, if objects group together under a filtration, they'll continue to group together under a coarsening of that filtration.