Okay so lets talk about genetics
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The red or ginger color is a DOMINANT one, on a X ("female") chromosome : Xo. If the cat is XnXn or XnY, it's any other color as dictated by the other color genes (Xn being the recessive "not red" allele).
If the cat is XoXo or XoY, then it's red. If it's XoXn (female) it's tortoiseshell.
SO... if you have a ginger cat, it means one of its parent is ginger or tortoiseshell (one of the parents must have the allele and as it's dominant it would show) ! As that wasn't in the bengal standard/ancestry, it means the litter has 2 fathers, one of them a ginger male
(I guess that would be the same for a serengeti).
So that's just a half breed, certainly not a full breed
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Of course you can have spontaneous mutations but they're rare
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Edit : on seeing again the photos... I guess the mother is a tortoiseshell as you can see a red spot on her head so there may have been only one (Bengal) father
. I'd bet anything that the male is the red one
.