Solvent dyes used as fuel markers — such as certain Solvent Yellow and Solvent Red grades — classify within 320419 based on their Colour Index designation, not their end use. No special import permit is required solely because of the fuel-marking application, but importers should ensure the CI number on the commercial invoice matches the applicable 10-digit tariff line, particularly for products enumerated under Additional U.S. Note 3 to Section VI.

Sulfur black dyes (CI Nos. 53185, 53190, and 53195) are water-insoluble colorants applied to cotton via a sulfide reduction process, primarily for low-cost black dyeing of denim and workwear. They are enumerated separately under 3204193000 because they were historically subject to trade-remedy proceedings that required precise product scope definition. Importers of sulfur black should confirm the exact CI number with the supplier to avoid misclassification into the NESOI residual lines.