What type of aircraft system would not be included in the MEL?

Aesthetic features like paint color are not included in the Minimum Equipment List (MEL) because the MEL is focused on items and systems critical to the safe operation of the aircraft. The MEL outlines which systems can be inoperative under certain conditions while still allowing the aircraft to operate safely and within regulatory guidelines. Aesthetic features, while important for the aircraft’s appearance, do not impact its functionality or safety and therefore are not listed in this crucial documentation.

In contrast, operational systems, safety equipment systems, and flight control systems are essential for the aircraft's performance and safety during flight. Any issues with these systems can significantly impact the aircraft's ability to operate safely, which is why they are closely monitored and included in the MEL.