This marble uses the gradiated twisted cane technique from last week's class to create a variant on the Ribbon Interior marble. The middle is Fossil Dark glass, with the transparents being Purple blending to Yellow on one face and Blue blending to Root Beer on the other. Instead of pulling this out into cane, it is twisted while maintaining spherical form, then finally shaped into a marble. The name is a reference to the classic mathematical conudrum The Four-Color Map Problem.