Im trying to identify the tree i have. Most of the leaves are a yellow with some green in the middle, over the last few years we have noticed new leaves growing that are all green almost like the tree is changing, most of this new green leaf growth is near the top branches of the tree. I'd like to keep the tree with the yellow leaves but am not sure if it will harm the tree? I've attached some pictures
Looks like Acer platanoides Drummondii. Common name variagated Norway maple. As the leaves open they will develop into a leaf with creamy white marginal band. http://www.diplomlandespfleger.de/Bilder/Baum/acerplatanoidesdrummondiiblatt.jpg Trees that have variagated leaves are slower in growth than the same species of tree with purely green leaves. You tree should only have the variegated leaves. Any shoots which show signs of reversion are best removed, (i.e. the plain green leaves) otherwise the variegated leaves will be overwhelmed by the stronger growing green.