I don't think it's necessarily better than clear, but I also think it doesn't make a difference. If you think about it, most lakes have a greenish tint to them already. However, I can see where using green fluorocarbon might have an advantage around vegetation. Overall, I don't think it makes a huge difference.
As far as brands go, I prefer Sunline FC Sniper. They make a green flourocarbon.
"If people concentrated on the really important things in life, there'd be a shortage of fishing poles." - Doug Larson