In a food processor combine the garlic, yellow tomatoes and bell peppers. Puree and thin with olive oil, vinegar to taste and some water if too thick. Season well to taste with salt and pepper.
Seed the squash and cut into 1/4-inch dice. Cut the bread into 1/2-inch dice, drizzle with olive oil, salt and pepper and bake in a 400 degree oven for about 10 minutes or until somewhat crisp and brown.
Ladle soup into chilled soup bowls; garnish with squash and croutons and center some red tomatoes and black olives in middle of each portion if you like.