Out of 6 discus, i got one pair.
in theory, u could get two.
your BD is recessive so it doesnt matter what it breeds with in ur tank, bc its genes wont be expressed in its children. (unless its another BD, then all will be 100% BD).
PB are dominant, so all the children will have PB expressed. (that is if ur PB's parents are both PB's: PP. but if it were cross PBxBD [Pp], then if it were to breed with the BD, 1/4 BD, 3/4 PB).
id say keep the strains to themselves. PB's breeding with any of the other strain mostly creates peppered fry, and the peppering often makes the fish look unattractive- meaning not many will want ur fry/pay high price for it.
also looking at the number of stress bars helps. (note that PB's dont have stress bars bc theyre a mutated strain). I breed leopard-snakeskins. They have 14 bars. all my fry have 14 bars, so there's a great chance that the fry will highly resemble the parents.
I think the wild types mostly have 9 bars.
-just let your discus pair by themselves.
-change of colors is normal. my discus 'know" me. they turn bright and approach the front and swim happily when im there.
But when a stranger comes by, (my gf), the discus will turn dark, show stress bars, and hide. the different colors show their moods.
they will also show more colors when its time to choose mates.
they will turn darker when their fry hatch and attach to them.
if ur discus hide forever in the corner and turn almost jet black, then you have serious a problem.
also at the 6-8 month you'll see dramatic changes in patterns start to finalize/appear in ur discus as they go from juvies to pre-adults? haha