What color on a map usually stands for water?
The colour of something is the appearance that it has as a result of the way in which it reflects light. Red, blue, and green are colours. 颜色
A map is a drawing of a particular area such as a city, a country, or a continent, showing its main features as they would appear if you looked at them from above. 地图
If something usually happens, it is the thing that most often happens in a particular situation. 通常
Colors on maps
Colors stand out from the map and provide identification to many features such as vegetation and water. Colors represent natural and man-made features of the earth.
Coupled with contour lines, colors add fabric to the features and terrain.
One of the principle colors is:
Blue = Water (streams, lakes, permanent snow fields and glaciers, etc.)