It depends what kind of map, but usually some form of water. This could be a lake, a river, an ocean or a reservoir.
Water represents a blue line on a map.
Blue on a map usually represents water. If it is a road map, blue is often the smaller roads.
The blue line on a map usually represents a stream of water!
a river
the Borders
Usually represent a stream, river, or other body's of water.
The blue shading on a map usually represent an area or body of water. Aquatic animals normally live in these areas on the map.
the blue line represents Lakes, Streams , canal and mainly just water
A stream,river or another body of water.
I assume you are talking about a political map. In that case it would be donkey or Democrat.
Blue on a map shows bodies of water. Other colors such as green and brown represent mountains and valleys. Red marks some roads and pathways.
The blue shading on a map usually represent an area or body of water. Aquatic animals normally live in these areas on the map.