panthers with red bars and blue bars and some inbetween...with genetics
yes it is possible to have both red bars to get some blue bar offspring, it depends how far the lineage of the panthers sires and grand sires..
if you continue breeding redbars with other redbars and continue doing so, the more chances the offspirng will have just redbars, same with blue bars
"true blue" nosy bes are not rare , pretty common, just alot of breeding of the bluest chams with other blue chams, and continues again...
"How blue" is different, some are just bluer than others, each cham is different
hope this helps