Fanfiction often bends the rules of the original Naruto universe. Naruto having a green Sharingan could be a really interesting concept. It could be that a powerful entity or some sort of ancient magic/technology in the fanfic world has bestowed this upon him. This could lead to new story arcs. He might face discrimination from those who know that the Sharingan is an Uchiha - only thing originally. Also, his relationships with Sasuke and other Uchiha members could take a whole new turn as he now shares a part of their special ability.
If Naruto had the Sharingan in fanfiction, it would likely lead to some interesting power - up scenarios. He could combine the power of the Sharingan with his own massive chakra reserves. This might make him an even more formidable opponent. His training would also take a new turn as he'd have to learn to control and master the Sharingan's abilities, like the different levels of the Sharingan and their unique powers.
It's possible in the realm of fanfiction. Danzo is a complex character with access to many secrets and resources. If he were to give Naruto a Sharingan, it would completely change Naruto's power dynamics. Naruto already has his own powerful abilities like the Nine - Tails' chakra, and adding the Sharingan would make him an even more formidable opponent. However, this would also bring new challenges for Naruto in terms of controlling the Sharingan's powers and dealing with the Uchiha - related baggage that comes with it.
One implication is that it changes his combat style. He can now use the Sharingan's abilities to predict enemy moves and copy jutsu more effectively. Another is that it might affect his relationships. For example, Sasuke might see him differently. Also, it could lead to new power - up scenarios and different training regimens in the fanfiction.
In fanfiction, if Naruto has the Sharingan, it can change his relationships. He might have a different connection with Sasuke, who is originally associated with the Sharingan. Also, it could lead to new story arcs. For example, he may need to learn how to control this new power, which could involve training with characters like Kakashi who also has the Sharingan. It can also attract the attention of different villains or groups who are interested in the power of the Sharingan.
It can also change Naruto's relationships. His friends might be in awe or even a bit scared of his new power. Enemies would surely target him more. Also, it could mean new story arcs. For example, he might have to deal with the dark side of the Rinne Sharingan's power, like being tempted by its overwhelming abilities. And he may need to find a way to use it for good without succumbing to its potential negative influences.
One implication is a change in his power level. The Mangekyou Sharingan gives access to powerful jutsus, so Naruto would be even more formidable. He might also face new enemies who are interested in his new ability.
One reason could be some sort of experiment. Maybe Orochimaru or another villain was trying to create a super - ninja and combined the genetic material of the Uchiha with Naruto's. Another possibility is that it's a gift from a powerful being. For example, a god - like entity could have bestowed the Sharingan on Naruto to help him in his quest to bring peace to the ninja world.
One implication could be enhanced power. The Sharingan already has powerful abilities like seeing chakra flow and predicting movements. A golden Sharingan might have even more advanced or unique powers. Maybe Naruto could use it to see into the future more accurately or manipulate chakra in a completely new way.
He might gain enhanced perception abilities, which would be a huge boost to his combat skills. With the Sharingan, he could predict his opponents' moves more accurately.
One potential implication is that Naruto's fighting style would change drastically. He would have to learn how to use the Sharingan's abilities like predicting movements and copying jutsus. This could make him an even more formidable opponent.