With Japanese maples there is a huge variety of genetic diversity within individual seats and the seats may be significantly different from the parent plant though of course some will be similar. You may have to plant quite a few to get the variety you want to grow. Seriously you may have a green form but it may produce mixed or red leafed seedlings, large leaved or fine leafed you just can't tell, that is what makes JM so interesting, very few other trees have the same genetic flexibility within one generation.