Maybe his non-sharingan blood had some effect on his sharingan. Who knows, since it's a bloodline limited thing, it could have easily changed to it's new owner. An evolution as you might, we alle know that at some point in history, the Sharingan was a new evolution of the Byakugan. And in other circumstances, things might adapt themselves.

Maybe it's a small evolution from the sharingan that would only be possible in other bodies. Because the needs of the sharingan couldn't be fulfilled in a non-sharingan body it adapted itself in a new enviroment. And that could explain the difference in sharingan.

maybe a bit far fetched