I can understand Sakura, but I will never get how Madara Uchiha the original owner of the Rinnengan can't even tell that Sasuke's eye is completely different from the rinnengan. How observant do you have to be to tell its FREAKING RED!!!
Also, the Sage probably has the 9T Sharingan sealed on his forehead.
Sakura ?????
She took it for the rinnengan as well. The Rinnengan is purple and I can see that she isn't the most knowledgeable about doujutsu, but i don't get how the differences got past Madara