It is in fact a Gretsch and I believe it is a White Falcon model but it is painted in a custom green color for exclusively for Bono. I heard somewhere he called it the "Irish Falcon".
Yes it's a custom guitar for like $3,000! its called the irish falcon, they copies are sold everywhere now. The two first original ones are owned by bono and the other one is owned by a guy who works at fender. Its suppose tosound beautiful but has a little problems with the imput jack, if you listen to Walk On at slane castle you'll here it. It's on my wanted list
I have heard people talking about it who own it and they say the guitar has a lil problem with that... you shouldnt have a problem with a guitar at that price...