Gustavo Dudamel, Herbie Hancock and an All-Gershwin LA Phil Gala   “So much blue,” said jazz legend Herbie Hancock, as he gazed out at the audience from onstage at Walt Disney Concert Hall. The occasion: the Los Angeles Philharmonic’s season-opening all-Gershwin concert, followed by the LA Phil Gala, “Rhapsody in Blue.” And like Hancock, I could see from my Orchesta West seat that many women all around the hall had beautifully color-matched their gowns to the gala theme. Hancock then settled down to his brilliant piano solos, while the L.A. Philharmonic’s music director, Gustavo Dudamel, conducted the orchestra....