Very nice bearded dragon you have there. It is very possible some sandfire or similar genetics worked their way into your dragon. It is also not unusual for a 'normal' looking dragon baby to grow up into a rather colorful and stunning adult. As all bearded dragons in North America came from the same original stock, some shared genetics will be present (limited 'fresh blood' tons of breeding means nearly all dragons in North America are related in some fashion). As Australia still (or at least I haven't heard of any changes) bans the export of all their native wildlife, very little fresh blood gets into North America. The only fresh blood entering the US was about a half dozen dragons imported from Europe a couple years ago.
That being said, giving how prolific bearded dragons are and how popular they have become, it is probably harder to get a completely 'normal' looking dragon these days. Not to mention a reddish/yellowish phase is common in the wild with inland bearded dragons which originated in the 'red/orange' sandy areas of Australia (which was concentrated upon by breeders to bring out as much intensity as possible...and out bred over the years to make many of the stunning color morphs we have available today).
This 'closed' bloodlines due to lack of fresh unrelated blood coming into breeding colonies is also why it is very important for people wanting to breed their dragons to ensure they are as unrelated as possible. (ie no direct sibling/parent, sibling/sibling, or sibling/grandparent matings etc). Though line breeding is done alot to concentrate desireable traits out breeding is needed to prevent concentration of harmful genetic mutations (ie small size, kinked tails, missing eyes/toes etc).
Sorry, meandered off a bit there...THough your dragon does have nice color and probably does have some sort of pastal, sand fire or whatever in its genetics, till you know for sure its parentage, probably best (if you do breed him in the future) to advertise the offspring as normal x (?) (where ? is the type of bearded dragon you pair him off with, whether normal or something else)
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PHLdyPayne