Susanoo theory

[Thetruekakashi]

So if it's silver it's probably because of his hair or something.

 

[Ageha Jaeger]

Kakashi's susanoo seems like a rare case because of his circumstances. It's almost like the susanoo takes on some of his physical features like the scar on its eye.

His might be the one exception to your theory. But it makes sense since he's the only non-Uchiha with a Susano'o.

 

[salamander uchiha]

Thats a pretty solid theory.
If naruto had Susanoo I guess hes would be green based on your theory
+ rep

No itd be a retarded colour because hes an idiot.