What kind of Japanese maple is it? When you refer to the "parent tree", does that mean this one is a seedling of a larger, established tree? If so, there can be considerable variability between the parent and the offspring with one often bearing very little resemblance to the other. And of course you do realize that Japanese maples come in a very broad range of leaf colors and that many selections go through a series of colors through the seasons, red being only one. And the amount of sunlight the tree receives can also impact leaf color, especially in midsummer.

Some reversion to green is normal in mid summer in many cultivars.

I bought it at a store. My parents(mom & dad's) tree has always had ONLY red leaves. I didn't know there were other kinds that turn different shades through the year. That must be what I have...I lost my paper that came with the tree. So I don't know what kind it is(cultivar). Thanks for responding! :)