To get a Killer Bee, both parents MUST have the pastel gene. Two Pastels provide a 25% possibility of a SuperPastel, which is part of what is required for a Killer Bee. The other part of a Killer Bee is the Spider gene. This means that at a minimum, one parent MUST be a Bumblebee to get a Killer Bee. It is genetically impossible to produce a Killer Bee without either a Bumble Bee or a Killer Bee as one of the parents.

To produce a Pied, both parents must be at least het for Pied. This means that to produce a Pied Killer Bee, one parent MUST be either a Bumble Bee (preferably a Killer Bee) AND either at least het Pied (preferably homogeneous Pied). The other parent MUST be at least a Pastel (preferably a Super Pastel) AND at least a het Pied (preferably homogeneous Pied).

Therefore, the "cheapest" possible parents of a Killer Bee Pied are:
Bumblebee het-Pied
Pastel het-Pied

Each offspring will have the following possibility of producing each of the following morphs:
1/32 Killer Bee Pied
2/32 Bumble Bee Pied
1/32 Spider Pied
1/32 Super Pastel Pied
2/32 Pastel Pied
1/32 Pied
3/32 Killer Bee 66% PossHetPied
6/32 Bumble Bee 66% PossHetPied
3/32 Spider 66% PossHetPied
3/32 Super Pastel 66% PossHetPied
6/32 Pastel 66% PossHetPied
3/32 66% PossHetPied

The odds are much better with a Bumblebee Pied and a Pastel Pied (no hets):
1/8 Killer Bee Pied
2/8 BumbleBee Pied
1/8 Spider Pied
1/8 Super Pastel Pied
2/8 Pastel Pied
1/8 Pied