I've had a bumper greenhouse tomato crop but most stubbornly refuse to ripen. Varieties are Coeue du Boeuf, Manacor and one yellow variety - Sunrise I think . Many of them turn pink with a yellowish hue around the top. Is it possible that the yellow variety has cross pollinated ? Cut them open and they are deliciously red and tasty and quite edible. Some remain stubbornly green and are unlikely to improve now that autumn is with us. Comments and suggestions would be welcome. A friend of mine has a similar problem of non ripening and we both live in the southwest where we have enjoyed a sunny summer.