pastel / spider = bumble bee
pastel / pastel / spider = killer bee

Since a parent can only pass 1 gene of a set to the babies, you have to have both parents with a pastel gene to pass along. So if the babie gets 1 spider gene from a parent and each parent passes along a pastel gene you get a supper pastel spider = killer bee.

When breading a killer bee it will always pass 1 pastel gene and 50/50 chance on passing a spider gene.