What color indicates an airport with a control tower on a sectional aeronautical chart?

The color that indicates an airport with a control tower on a sectional aeronautical chart is blue. This color coding helps pilots quickly identify which airports have air traffic control services available. The use of blue is consistent across sectional charts, providing a clear and standardized way to communicate important information about airport operations. Airports depicted in blue signify that pilots can expect assistance from a control tower, which implies more structured air traffic management compared to those without towers, thus enhancing safety and efficiency during flight operations. Understanding this color distinction is critical for navigation and planning during flight.