The guitar played by Kurt Cobain for Nirvana’s breakout 1991 single “Smells Like Teen Spirit” video has sold for $4.5 million at auction, the sellers said Sunday. The 1969 Fender Mustang Competition Lake Placid blue finish electric guitar was expected to fetch a more modest $600,000, said the seller, Julien’s Auctions. But Indianapolis Colts owner and CEO Jim Irsay plunked down a lot more, not least of all because a chunk of the proceeds will go toward benefiting mental illness. Cobain shot himself in 1994. “I am thrilled to preserve and protect another piece of American culture that changed t…