Line baking sheet with wax paper, and coat with vegetable cooking spray. Using pecan halves, form 12 turtle shapes on baking sheet.
In 1-quart microwave-safe bowl, combine caramels and milk. Microwave on high 2 minutes. Stir in chopped pecans. Quickly pour caramel mixture on top of each turtle.
In microwave-safe bowl, melt semisweet chocolate 1 minute on medium, stirring halfway through. Spoon chocolate on top of caramel-nut mixture. Let set in refrigerator 45 minutes.
In microwave-safe bowl, melt white chocolate 30 seconds on medium, stirring halfway through. Transfer melted chocolate to resealable plastic bag. Snip one corner off bag, and drizzle turtles with white chocolate. Top with green candies. Store in airtight containers.