Pipe marking color Orange corresponds to which substance?

• A. Seawater
• B. Lubricating Oil
• C. Hydraulic Oil
• D. Diesel

Answer: (C)

Pipe color coding on Navy ships is used to identify what a pipe carries at a glance. In this system, orange is reserved for hydraulic oil lines. This helps technicians quickly recognize the fluid as hydraulic oil, which is used to power and control actuators and other components under pressure. The orange cue keeps hydraulic systems distinct from seawater, lubricating oil, or diesel lines, reducing the risk of cross-contamination and guiding the proper safety and handling procedures. So orange corresponds to hydraulic oil.