Well thats good to know c4al from here too is a convert and and has know been showing nice fish for a couple of years with the BLA.
Talking to the people and buying from BLA events are the best way to get 99% sure true pairs. If the judge suspects it's not a true pair the fish will be disqualified in the October show/auction. but this is very rare most good breeders are keen to share there jean pool about, this way if something happens you can at least get the right fish back later.
As for crossing, if you start with a Pink like you have with then panda then crossing with a normal gray would result in in only gray fish. However the top colour will affect the cross, F2's will then produce some Pink fry.
Crossing with other recessive base colour's like blond, yellows, blues, gold, albino or lutino can resualt in double recessive base colours which are white, silver and creme but these are extreamly rare to see. Not something to aim for at first but lurning about all these things will give you an insight into the world of guppies.