A solvent dye is a dye soluble in organic solvents. Solvent dyes are used to color organic solvents, hydrocarbon fuels, waxes, lubricants, plastics, and other hydrocarbon-based nonpolar materials. Fuel dyes are one use of solvent dyes. fuel dyes are used in automotive industries to colour petrol fuel and other hydrocarbon based fuel oil. now solvent dyes is vastly used in plastics.