Getting the best looking Morph/combo offspring is more likely to happen if you start With the best looking parents...Selective breeding.
You don't start with average animals when breeding for quality no matter what kind of animals they are...Dogs, Cats, Horses, Snakes... That is why people pay top dollar for top animals so they have Top genetics passed on to every animal they produce.
OP - That is a nice looking bee the brown out on top may get darker but it I don't think it will spread... I have noticed that the brown out on pastels I have raised stays pretty much to the scales that have already browned and doesn't spread over the nice clean yellow ones, though the Yellow can fade with age.