Which color indicates the presence of sewage?

The presence of sewage is indicated by the color black. This color is commonly associated with waste materials, including sewage, and is universally recognized in various contexts, such as plumbing and environmental science. Understanding this color code is essential for effective waste management and safety practices, as it alerts individuals to the potential hazards associated with sewage materials.

In many systems, yellow often signifies caution or a warning but is not specifically linked to sewage. Green might indicate environmental safety or cleanliness in other contexts, while gold is not a standard color used to denote sewage. Therefore, black is the correct choice because it conveys the direct message of the presence of sewage effectively.