Do some googling - breeding morphs is all about genetics. Learn what heterozygous (het) and homozygous means. Familiarize yourself with the terms dominant, recessive, co-dom, etc., and learn which morphs are what.

For example, pastel is a dominant trait. If you crossed it with a normal ball python, you would get 50% pastel babies and 50% het for pastel babies.

It's about math and selective breeding