i would guess that the colors have to be in the water for that equasion... i would also guess that it's not an exact science.

that said 3 ft give in either direction the fish is gonna smell it. provided you have a fat juicy worm on there.
ive heard but have not tried that some people stuff the tube with a sponge or some kind of absorbing material and then squirt some bunker oil into the tube for a good scent. I don't know how long the scent would last but it sounds like it should work pretty good. I keep meaning to try it but just haven't gotten around to it yet.