Fly line color can be an important matter, especially in technical fisheries. I tend to stay away from neon fly lines which can send fish into hiding. There are plenty of fly lines available in muted colors like moss green to help hide them on the water. While they may not be as visible, the extra fish you catch make it more than worth it. If you are using a bright-colored fly line, fishing a leader 9 feet or longer can help trick more fish.