A color for every environment
But an orange ball is not always easily visible in all places. For example, think about all the places in the U.S. where you can see the well-known rust-brown rock in mountains and valleys? Against such a background, an orange ball is not very useful at all. That is why the rule is to pick the color that is most fitted for a specific environment. As a result, you can see red, orange, yellow, and even white balls dangling from the lines.