Abraham Lincoln, taken by Civil War-era photographer Mathew Brady in 1861, at the beginning of Lincoln's first presidential term:
A colorized image of three Confederate prisoners and its original black and white stenograph, taken by Mathew Brady in 1863 on top of Seminary Ridge in Gettysburg:
And here's Custer:
More at Daily Mail and at the artists' Facebook page Colorized History. This related book gets excellent reviews: The Civil War in Color: A Photographic Reenactment of the War Between the States.