It was clearky stated to be a Sharingan. Why is it ppl in my threads keep sayin she had a Sharingan? Kaguya has no relation to Rinnegan, nor had it. Only The Sage, Madara and Sasuke have ever unlocked Rinnegan.
Her eye is called the Rinnesharingan. Obviously, both the Sharingan and the Rinnegan are derived from that eye. Though she may not have all the powers of the Dojutsu her eye gave rise to, it is still the origin of such.