As for the band, usually it's gold, white gold, or platinum. It's a good idea to see what kind of jewelry she already has so that you can be sure it matches, but if you're completely clueless, silver is a safe bet. Print this SYW out, take it with you to the jewelry store, and buy the perfect engagement ring. Once again, we reiterate that you don't have to spend so much that you have to sell a kidney. We're sure it'll last forever, but just in case, keep the receipt.
Rings are returnable.
Tattoos are not.