"Blue lines" often refer to the blue markings used in various contexts, such as sports fields or roadways. In sports, blue lines are crucial in games like ice hockey, where they help define zones on the rink. They indicate where players can enter the offensive zone and are essential for understanding game rules. In urban planning, blue lines can also represent water bodies on maps, such as rivers or lakes. These lines help in identifying water resources and are important for environmental management and city planning. Understanding blue lines in both contexts aids in navigation and strategic planning.