This coming October, the $100 bill will have new security features to help deter counterfeiters. These include a 3D security ribbon woven into the paper with animated and color-shifting watermarks. If you were to examine the new $100 banknote, you'll notice a color-changing bell hidden inside the inkwell (located to Franklin's right side) that turns from copper to green as the bill shifts.
Know more about it
here.