When you purchase most peaches in a large grocery store chain, they tend to be rather hard and will not taste the same as a tree ripened peach. The reason for this is that tree ripened peaches are very fragile and do not ship well. Most commercial peach growers will pick them firm and usually under ripe. The reason for this is that peaches will travel two weeks on average from grower to the produce aisle. That means the peaches aren't allowed to develop that full and sweet peach flavor.
I have 6 peach trees at Fox Farm and I planted different varieties that produce at different times of the year. I allow them to remain on the tree until they are completely ripe and soft. What happens that the sun will make parts of the peach red, but the leaves will leave shadows on the leaves. This doesn't happen with commercial peaches because they aren't left on the trees long enough for this to happen. I call them flames. I have attached a couple pictures of peaches from last years crop and you can clearly see the outline of the leaves where the sun was blocked. This doesn't mean the peach isn't ripe in the shadows, the peach will be fully ripe. It makes for a very pretty peach.