I read something once by Frank Johnson, the owner of Moldcraft lures. What he basically said was that he only needs 4 standard colours to go trolling for pretty much anything - blue/white, pink/white, green/yellow and red/black. All the other colours were to attract anglers because the lures have to catch anglers before they have any chance of catching fish. I think that he's about right although I also like plain black lures and have caught plenty of fish on them.
GD - I always mean to check out the difference (to my eyes) between fluorocarbon and regular mono but I always forget to take some with me. I'd be prepared to accept that it makes a difference with lower diameters but I'd take some convincing that a marlin, that needs sharp eyes to make a living, can't see 400# leader, fluorocarbon or mono.
PS I did take a shark rattle diving with me once and it didn't sound at all like I expected. It didn't rattle at all, just made a sort of metallic "swooshing" sound as the ball bearing ran backwards and forwards. I don't know what a shark thinks they sound like but they do work.