A. You can pick peaches when the color begins to change from green to yellowish green or even beyond. I prefer to wait at least until the color has solidly changed from green to yellow but are still firm.
At this stage they will continue to ripen after they are harvested if they are kept at room temperature. They will develop better flavor if left on the tree as long as possible. If birds are not a problem then I prefer to leave them until the fruit has changed color and the flesh has softened just a little bit from being hard as a rock.
At this point, the birds are looking at them and not quite sure if they want to peck them or not. This is the stage also when some of the more hungry birds will peck at them anyway. When I first start to see bird damage I know I’d better get them off the tree.