Multicombination / Multikombine / x.Mult / I-M-L?
These are individual parts (or pre-assemblies) that have more than one color, whether it's marbled or overmolded or assembled at the factory. This does not include print colors.
The numbering on these is confusing. There are several numbers (1.Mult, 2.Mult, etc.), possibly corresponding to the first, second, etc. time that part has appeared as a Multicombination.
They also correspond to the standard numbering system, though. For example, color IDs 30, 31, 32, 33, 80, and 81 are Multicombination colors (I'm not sure which x.Mult they match up with, though). These could potentially fill the gap between 50 and 99.