Louisiana Revised Statutes — Title 47 (Revenue and Taxation)
La. R.S. 47:1684 — Issuance of special invoices; coloring of gasoline
Every dealer selling gasoline to be used for refundable purposes shall issue the special invoices required by R.S. 47:1682 and shall at the time gasoline is sold and prior to delivering the invoice to the purchaser dissolve in the gasoline, except aviation gasoline sold for operating or propelling aircraft, a quantity of dye sufficient to color the gasoline to meet such requirements as may be prescribed by the collector of revenue.
Source: official text