I was lucky enough to get a loose Brontosaurus (dino only) for about 35$ only. After getting the toy, the seller told me he has another one which he kept for himself as he preferred the colors... I asked for pics and he sent them. Indeed, the one I got is more on the greyish side, while his is more of a brown shade. I was unaware the Bronto had color variants, even the official page doesn't list them... anyone knows more?
Here is my Bronto, with the grey stripe accross his back and sandy brown sides:


And here's his toy, with the more reddish brown sides and less grey.


Anyone knows the origin of this variety?