How can personnel identify a fuel truck under airport operations?

Personnel can identify a fuel truck under airport operations primarily because it is marked with specific signage indicating it is for refueling operations. Such signage is crucial for safety and operational awareness on the ramp, as it alerts all airport personnel and other ground vehicles about the truck's function. This identification aids in maintaining safe distances and protocols during refueling operations, which can be hazardous if not properly managed.

While the other choices may contribute to the identification of the vehicle in other contexts, they are not as reliable or standardized as the use of specific signage. GPS tracking systems, unique color schemes, and specialized refueling equipment could be present on various types of vehicles but do not universally signify a fuel truck's role, making them less effective for operational identification on the airport ramp.