Fuel dyes are dyes added to fuels, as in some countries it is required by law to dye a low-tax fuel to deter its use in applications intended for higher-taxed ones. Untaxed fuels are referred to as "dyed", while taxed ones are called "clear" or "white".
Aviation gasoline is dyed, both for tax reasons (avgas is typically taxed to support aviation infrastructure) as well as safety (due to the consequences of fuelling an aircraft with the wrong kind of fuel).
A fuel tax (also known as a petrol, gasoline or gas tax, or as a fuel duty) is an excise tax imposed on the sale of fuel. In most countries, the fuel tax is imposed on fuels which are intended for transportation. Fuel tax receipts are often dedicated or hypothecated to transportation projects, in which case the fuel tax can be considered a user fee. In other countries, the fuel tax is a source of general revenue. Sometimes, a fuel tax is used as an ecotax, to promote ecological sustainability. Fuel taxes are often considered by government agencies such as the Internal Revenue Service as regressive taxes.
Fuels used to power agricultural vehicles, as well as home heating oil which is similar to diesel, are taxed at a different, usually lower rate. These fuels may be dyed to prevent their use for transportation.
View the full Wikipedia page for Fuel taxSolvent Yellow 124 is a yellow azo dye used in European Union as a fuel dye. It is a marker used since August 2002 to distinguish diesel fuel intended for heating from a higher-taxed motor diesel fuel. It is added to fuels not intended for motor vehicles in amounts of 6 mg/L or 7 mg/kg under the name Euromarker.
View the full Wikipedia page for Solvent Yellow 124