If you buy peaches look for ones with a creamy to gold undercolor that indicates ripeness. The amount of red on peaches depends on the variety, it is not always a sign of ripeness. Find fruits that have a well-defined crease and a good fragrance. Peaches with a green undercolor are not ripe and will not ripen because peaches and nectarines only ripen well on the tree. Peaches are ripe when they give to gentle palm pressure.
Green coloring indicates immaturity.
Shriveling at the stem end or excessive softening are indications of overripe peaches. You can keep peaches and nectarines for one to three days but you have to be very careful, one small bruise and it will go bad on that spot. Firmness and days from bloom can also be used to estimate maturity. For more information on apricots and nectarines click here. To check for ripeness press gently near the stem end.