The graft is probably either below the soil level or very smooth so you can't see it. The red leaves will be coming from the scion (the top part of the tree which is grafted onto the rootstock) and the green from the rootstock. A green leaved rootstock can't produced both green and red leaves and nor can a red leaved scion. You could dig out suckers and provided they have some roots they should grow. However, red leaved shoots coming from the scion will probably not have any roots.

Thanks Flora UK!