Patience. I go thru this every year...last year, we had hundreds and hundreds of green tomatoes that seemed to have no interest in turning color. I told my wife that with our luck; they were ALL going to turn at once. A couple of weeks later; I called her at work and asked if she remembered that comment. When she said 'yes', I replied 'today's the day'. Mine are ALL heirlooms/open pollinated, they are trellised on cattle panels, and they seem to take forever every year.
Well, that will make canning easier lol!