Solvent dyes (used in petroleum products, waxes, and plastics), fluorescent dyes not meeting the brightening agent definition, and proprietary mixed-class preparations that combine dye types from multiple subgroups are the most frequent entries. Novel chromophore chemistries that postdate the classification schedule's drafting also tend to land here pending a more specific ruling.

A binding ruling from CBP is advisable when a preparation contains a mixture of dye classes, when the colorant's application mechanism does not clearly match any named dye class, or when the importer is uncertain whether the product's essential character is the dye substance or an auxiliary component. A ruling provides legal certainty and protects against reclassification penalties on future shipments.