Motiv at one time was rumored to be going with a military type theme with some of their balls. You have the sniper, tank, and to a lesser extent the raptor.
Olive drab isn't the number one color people would pick for a bowling ball. However, if you were going with the military theme and had a ball named "Tank", what other color/color combination would you choose? The design on this is reminiscent of WWII imagery, thus making it a win in many peoples books.
Besides, I willing to bet those buying the ball are getting it because it is a Motiv urethane more so than a military themed ball.