Why is the leopard gene more dominant than others?

[asplundii]

Leopard is a pattern and color mutation. The leopard tends black in the pattern.

So for your Leopard Ivory example. The Leopard changes the pattern in the Ivory, which would usually go unnoticed since the Ivory is such a strong color mutation. However, since the leopard adds "black" to the patter, think darkness, this is why the purple patterns POPS in a Leopard Ivory...



.... I think.

It is more accurate to say that Leopard (and also YB) are pigment distribution mutants and that Leopard returns a level of pigment distribution to the large-scale removal that Ivory causes. This return of distribution generates the shadowing you see in the Ivory Leo