What color is a tennis ball? (don't cheat!)

[dtbog]

When someone asked me this question today, I looked at him like he was a complete idiot. 'What color is a stop sign?' I joked. 'What color is the tip of a black marker?' etc etc.

Apparently there is more than one knee-jerk reaction to this question... yes I know that you can make a tennis ball in any color and that there are different kinds of tennis balls.

When you think of a tennis ball, what color is the ball that pops into your head?