They wanted to use an American tank, but weren't allowed—that's why the American team exhibiting at the Venice Biennale used an overturned British tank for their treadmill masterpiece, Track and Field, instead.
What's the best way to sneak up on an enemy? Staying invisible. What's a material which could help something as large as an armored vehicle camoflage with its surroundings? E-ink. Yes, the very same technology that's used in ereaders.