Since the different wool and dye types are now different materials in 1.13, it might make sense to remove the long-time deprecated magic wool/dye data values in DyeColor and instead provide a direct mapping to the corresponding wool/dye materials.
Or keep both for types of mappings for the time being, until plugins had some time to update (since there wasn't an alternative to using these magic values previously: actually, plugins were able to use the Wool MaterialData class for this, though I assume many were/are still using the data values directly).

Example use case: Mapping from sheep color to corresponding wool type. In this case minecraft seems to do this via a direct mapping as well.