What color were Abraham Lincoln's eyes?

President Abraham Lincoln's eyes were described as gray by those who knew him personally, including his wife and his niece, according to the Lincoln Institute. Its Abraham Lincoln's Classroom website references "The Inner World of Abraham Lincoln," by Michael Burlingame, which contains quotes from Lincoln's niece.

In his book, Burlingame includes writing by Lincoln's niece regarding an interaction between her aunt and uncle: "When Mary slyly poked fun at him for committing some faux pas he would look at her quizzically, his gray eyes twinkling, as if to say, ‘How can you attach such great importance to matters so trivial?’"