What color on a military map indicates hydrography or water features?

The color blue on a military map specifically indicates hydrography or water features. This includes rivers, lakes, streams, and other bodies of water. The use of blue is standardized in military mapping conventions, making it easily recognizable for users who need to identify water sources during planning and operational phases.

In contrast, other colors on military maps have different meanings: black typically represents man-made features like roads and buildings, green represents vegetation such as forests and fields, and red is often used for roads and populated areas. By using blue for hydrographic features, maps convey essential information clearly and efficiently, which is crucial for navigation and mission planning.