Solvent dyes are a class of non-ionic dyes that are soluble in organic solvents—such as alcohols, ketones, esters, and oils—but insoluble in water. They offer bright colors, excellent transparency, superior solubility, high stability, and good light and heat resistance. Solvent dyes are widely used in plastic coloring (e.g., PS, PMMA, PET), inks (printing inks, marker pen inks), coatings, wood staining, and coloring of gasoline and lubricating oils.