I'm the Music Man, music you bananas!

Things I don't understand:

(If you have the answers to my queries, please PLEASE comment or email me!!)

1) Where does brown come from? I don't recall seeing that extra 'B' in ROY G. BIV. Is it possible to get brown light through a prism? Probably not. I could be wrong, but it seems to me that brown is a physical impossibility.
2) When you put your finger under the faucet, the water moves toward your finger instead of being pushed away. What gives? I'm sure my finger has more gravitational impact on the water, being more dense, but I'm pretty sure that my finger isn't attracting that water. I should be poking the water away from myself, but instead it just runs down my arm. Why?
3) Why is the guitar the major instrument in every rock band? Are they the most versatile? Does the guitar epitomize beautiful music? How and when did they become so popular, and what did they replace?
4) Call me an idiot, but I can't understand the basic idea of stocks. People decide to say that they have a magical 100,000 "shares" and people buy them, and then sell them to other people, who in turn sell them to someone else. Whoever decided to make and sell stock has just made a profit and it cost nothing. No production, no tangible evidence of a purchase? How does the investor know that it is even worth anything? It's just an imaginary, arbitrary... nothing that people pay for the privelege of saying they have?
5) Where does the idea of Holy Water come from? I have read the Bible cover to cover, and I know that it doesnt say anything about Holy Water. I know that the old pagan customs of Britain and Gaul included sanctifying water and banishing the evil spirits, is it some sort of weird tie-in that the Catholic church used to help ease the transition from paganism to Christianity? Holy Water seems like a pretty... un-Christian concept that Christ never endorsed.

That's all for this time, I'm sure I'll stumble on more enticing conundrums later on.