D.C. Mun. Regs. tit. 16, r. 16-1707
Each gasoline station shall have a color-coded chart that clearly identifies which color represents each octane rating. The colors used shall comply with the then-current version of American Petroleum Institute (API) Recommended Practice 1637, "Using the API Color-Symbol System to Mark Equipment and Vehicles for Product Identification at Service Stations and Distribution Terminals."
The color-coded chart shall be conspicuously posted in or upon the premises so that it may be readily seen by the DCRA inspector, DCRA investigator, or person(s) delivering fuel without requiring the person(s) to enter the premises (i.e. posted so that the chart can be viewed from the exterior of the kiosk or store).
The fill pipe and/or access cover for each underground fuel-storage tank shall be painted to match the appropriate octane rating color from the color-coded chart.
D.C. Mun. Regs. tit. 16, r. 16-1707