What color does a real $100 bill turn?

How to Spot a Real $100 Bill by Its Color-Shift Feature

One of the most reliable ways to tell if a $100 bill is authentic is by checking its color-changing ink. On a real bill, the numeral “100” in the lower right corner of the front side isn’t just printed in a fixed color—it actually shifts when you move it.

Hold the bill under a light and slowly tilt it back and forth. If it’s genuine, the copper-green number will transform into a rich, deep black. This color-shift effect is no accident—it’s a sophisticated security feature designed specifically to foil counterfeiters.

Fake bills usually fail this test. Most counterfeits either lack the color-changing ink entirely or use ink that can’t replicate the real thing. That means the number stays a dull copper-green no matter how much you tilt it. No shift, no authenticity.

This feature, along with others like the 3D security ribbon and watermark, makes the modern $100 bill one of the hardest to copy. Still, many people overlook it, assuming all fakes are obvious. In reality, some counterfeit bills look convincing at a glance—but they almost never get the details right.

So next time you’re handed a $100 bill, take a second to check the bottom right corner. Tilt it. Watch for the change. If the color stays the same, it’s likely not real. That quick glance could save you from accepting a fake.