The appearance and flavor can be enhanced by temporarily removing the breasts from the marinade after they are nicely chilled, then either grill very fast over a super-hot grill (need a fine grate to avoid losing any through the gaps), or lightly brown them with a quick super-hot broil. The goal is to give the surface a bit of char and flavor without cooking the interior. Put them right back in the marinade bag and into the fridge to be fully chilled again before assembling your kabobs.
If you prefer to broil your kabobs in an oven rather than grilling, consider adding a dash of liquid smoke to the marinade. Do not overdo this though, it is strong stuff. Enjoy!