Combine mayonnaise, green onion, vinegar, mustard, relish, granulated onion, salt, black pepper, and granulated garlic in a bowl. Taste for flavor and adjust accordingly. Remember that potatoes soak up a lot of salt, so keep this in mind. Add egg and potatoes and fold into mayonnaise mixture. Scoop into serving dish and garnish with quartered eggs, a sprinkling of paprika (optional), and the reserved green onion slices. Cover and place into refrigerator for 2 hours before serving.