Soak 16 bamboo skewers in cold water for 30 minutes. In a blender, puree lime juice, garlic, red onion, salt, pepper and olive oil. Place all vegetables in a large bowl and pour marinade over. Let marinate at room temperature one hour, then drain vegetables. Place vegetables on skewers in a festive manner, alternating colors and shapes. Heat grill to medium high. Brush grill well, then wipe with oiled paper towel. Place vegetable skewers on grill and cook a total of 8-10 minutes to desired doneness, turning occasionally. Remove from grill and serve.