The giant Salmonflies of the Western mountains are legendary for their proclivity to elicit consistent dry-fly action and ferocious strikes.
Dyed lines make an enormous difference over spooky fish.
I don't believe the color of the fly line makes one iota of difference.
But I can say that on the majority of quality wild trout water in the East, fishing a leader in the 12-15 foot class is not practical most of the time.