Heat oven to 350°F. In large bowl combine the cake mix, butter, egg and 10 drops of green food dye at low speed until the entire mixture is crumbly and moist. Press the mixture lightly into the bottom of a 9×13 pan. Bake for 20 minutes at 350°F. Remove the pan from the oven and sprinkle with marshmallows. Immediately return the pan to the oven and bake for an additional 3 minutes, or until the marshmallows just begin to puff. Meanwhile, add the corn syrup, butter and white chocolate chips to a large saucepan and place over medium-low heat. Cook, stirring constantly, just until chips are melted and the mixture is smooth. Add the vanilla and salt to the mixture and stir. Remove 1/3 cup of the Lucky Charms marshmallows from the cereal and set aside. Remove the saucepan from the heat and quickly stir in the cereal. Immediately spoon the warm topping over the marshmallow layer, spreading to cover. Quickly top with the 1/3 cup Lucky Charms marshmallows and press them down lightly. Chill the bars until they are completely cooled. Cut and serve. Store leftovers covered.