Compliance is dictated by the APWA (American Public Works Association) Uniform Color Code. For example, Blue is for Water, Yellow for Gas, Red for Electric, and Green for Sewer. You must ensure the supplier uses lead-free, organic pigments that will not fade or leach into the soil. The printing should be encapsulated between film layers to prevent the warning message from scratching off during installation, ensuring the text remains legible for the entire service life of the utility line (often 30-50 years).