Very cool snakes. The male is amazing, and the female has a lot of black coloration. I've never seen the black and yellow phase for sale or in person. I hope they breed for you.
It definitely seems as though there are two definite color phases of sulphureus, the yellow and black, and the yellow and green. Mine are the yellow and green phase and they are from Surinam. There are supposedly two subspecies with sulphureus; Pseustes sulphureus dieperinkii, and Pseustes sulphureus sulphureus.
Could the two color phases differentiate between the two subspecies?

-----
Roy Blodgett
Green Man Herpetoculture
royreptile@yahoo.com
1.1 Drymarchon corais
1.1 Pseustes sulphureus
1.1 Masticophis taeniatus taeniatus
0.0.1 Coluber mormon
1.1 Lampropeltis getula californiae (desert phase)
1.0 Boiga dendrophila dendrophila
1.1 Corytophanes cristatus
1.2 Varanus acanthurus brachyurus (Mt.Isa)
2.3 Pogona vitticeps (snow and red/gold)
1.0 Iguana iguana
“All men lie enveloped in whale-lines. All are born with halters round their necks; but it is only when caught in the swift, sudden turn of death, that mortals realize the silent, subtle, ever-present perils of life.”- Herman Melville