Impa is the only real Sheikah we've ever seen, correct? We can also assume this is the case for Zelda. If that's so, who's to say they have to have red eyes and tanned skin? When Zelda took up the persona of Sheik, she most likely based it off of Impa. So she had red eyes a tanned skin as well. But can't red simply be a natural eye color in Hyrule? There's lots of speculation people like the Mask salesman and the skulleta... people (forgot their names) are in fact Sheikah. But can't that be their natural eye color? What I'm really asking is this: Is there any other proof all Sheikah have red eyes except for Impa?
Do you remembert the old lady in the Hideen Village (TP); she had red eyes and white hair (though there is the obvious possibility that it was due to aging) and the Village is suposedly the original Kakariko that was founded by the Sheikah.
Honestly, I've never realized that Sheikah's had red eyes, save for Sheik. But what are you saying abotu Zelda? That she's the only Hylian we've actually seen?
But don't forget, the Rito's also have red eyes, if I remember correctly.
And Mikaudes, her name was Impaz. Supposedly she's a descendant of Impa, or something.