MbMb/nMb
Marble is a marking that comes in two layers, the outline must always be darker than the base (or even black!) while the inside can be darker or lighter than the base.
Shapes and thickness can vary, generally it looks splotchy or swirly, some speckles are allowed to be scattered around (But do not exaggerate!)
You can take inspiration from marble cats or ball pythons
In dominant form you can use up to 3 colors for the marking, the outline must be always darker than the base, while the inner filling should go from darker to lighter.
When the marking touches the eye, it can color it! The color must follow Crystal Eyes rules!
For the border
For the filling
Non-dominant (nMb)
The inner layer of marble should always be filled as much as possible, small gaps are allowed but keep in mind that the filling should be recognizable at glance, otherwise it will look like Toxin