Each APWA color is assigned a standard frequency in the 3M™ Electronic Marking System (EMS) Warning Tape 7900 Series.
🟨 Gas → Yellow → 53.9 kHz
🟧 Telecom → Orange → 48.8 kHz
🟥 Power → Red → 34.9 kHz
🟦 Water → Blue → 73.5 kHz
🟩 Wastewater → Green → 41.4 kHz
🟪 Reclaimed Water / General Purpose → Purple → 44.9 kHz
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