It’s all about visibility in the water. You might choose a line color that makes it easier for you to see. Or, you might choose a line color that makes it more difficult for the fish to see. Both monofilaments and braided lines can be colored. Some anglers use yellow for clarity, to see when they’ve got a bite. Others use red or green in the hope that it hides the line from the fish. Fluorocarbon line is often not colored because it has a refractive index almost the same as that of water. This makes it very difficult to see anyway. Whether the water is muddy or clear seems to make little difference. Pink fluorocarbon line is claimed to be even better than clear – and oddly, it becomes almost completely invisible at some depths. As with most things fishing-related, if you talk to two different anglers about the same issue, they’ll probably disagree. But one thing is certain: clear versions of all types of fishing line remain popular.