The chances are better if both parents are red in color. But that is not a guarantee of adult coloration. But that would be the best way of getting a "red" one for certain. At times when they are imported they all look the same as neonates.
I think the colors are inheritable but most Sumatrans carry the genes for all 3 color phases.
With this being said I would strongly suggest getting babies from the brightest red parents you can find and this will greatly increase the odds of the ontogenetic color change landing in your favor.
While I was shopping for a red one I wasn't upset with what I ended up getting except for one of them being improperly sexed and me having 2 males which will make me eventually get a female.
So next time I will buy from a breeder with bright red parents so maybe I can get 1 of each color.
They where fairly aggressive as neonates (doesn't bother me) but as they got older and more used to me their aggression subsided.
Snakes are not "mean" as one finds in people. Their aggression is based on what they perceive to be a threat of some kind (i.e.. predation). So once they loose that fear, the aggression goes away along with it.
Both my adults can easily be handled, they still huff and puff a little when first startled, but that it.
They where little buggers as neonates though. Never seemed to get tired of biting me.
They tamed with little to no handling, just getting used to my presence around them broke their behavior patterns all together in regards to biting me. Therefore I believe most snakes with an aggressive reputation can be tamed in this manner even without a regular handling schedule as people often tout as a way of taming a snake.
I have been studying aggression in Reptiles and Amphibians for over 25 years.
I must say I procured many many nasty snakes because people didn't want them. Only had one Python reticulatus that would not calm down in the early 80's. I do however attribute this to feeding him a wild squirrel that almost killed him when he was like 2.5 feet long and I was 12 years old at the time. Yes my first Python was a reticulated python at age 11.
Back then no one kept those snakes except for 2 other people I knew. I was working in a pet store at the time and ordered him cause the owners son whom was 18 had one and I had to get one out of some kind of man boy envy I guess. plus as a young reptile freak, it was the "largest python" in the world as well.
Needless to say he topped out at 14 feet and lived 14 years as he was killed by the same 18 year old's adult female in 1995.
We didn't get as pair to breed them or anything, just fate had it that was.
He sired 96 babies in that first clutch, the female was over 25 feet long and laid many small eggs. Most peoples retic's lay 30 to 35 eggs and that's it. His female was the ones you read about in books that lay 100 eggs.
Enough blabbing about that.
Blood Pythons are a pleasure to own and work with and do not deserve the reputation that has been tagged onto them by the herp and science community.
I am sure from working with wild caught adults that this is where that reputation came from.
With the captive breeding of this species going on these days, one can procure a neonate that may be tame already.
If not they still tame down in the manner I stated as long as they become accustomed to your presence and loose that instinctual fear that helps them survive in a wild ecosystem where such behavior is essential to their ultimate survival in the web of life and the cycle of nature.
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Roberts Realm Of Reptile Research
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Thanks,
Frank Roberts

I opened my mouth and out flowed a melody black.