If you have the servos connected to the CMUCam board then you just have to jump the pan/tilt reverse jumper but if you are using the RC then you need to edit the code in tracking.h.
Code:
// If your camera suddenly moves away from the target once
// it finds it, you'll need to change the sign on one or
// both of these values.
#define PAN_ROTATION_SIGN_DEFAULT -1
#define TILT_ROTATION_SIGN_DEFAULT +1