FAA AMT (Aviation Maintenance Technician) Airframe Practice Exam

Seals used with a mineral base hydraulic fluid are identified by a blue dot or strip. This is because blue is the designated color for identifying seals in systems that use mineral base fluids. The other options are incorrect because they either use the wrong color or do not specify the correct type of fluid. For example, red is used for seals in systems that use polyglycol base fluids, green is used for seals in systems that use synthetic base fluids, and yellow is used for seals in systems that use phosphate ester base fluids. Therefore, the correct option is B, as it correctly identifies the color code for seals used in systems with mineral base hydraulic fluid.