Preheat oven to 350 degrees. Grease an 11×7-inch or 9×9-inch baking dish.
Prepare sugar cookie mix according to directions on package. Add the zest and juice of the lemon and lime and mix well. Pour the mixture into prepared baking dish and bake for 30 minutes or until done. Let cool.
Once cookies are cooled, break apart into a large mixing bowl. Add cream cheese and beat well until smooth. Roll into balls and place on a cookie sheet lined with waxed paper and place in refrigerator for 1 hour.
When ready to complete truffles, place dark chocolate in a microwave safe measuring cup. Melt on high in microwave in 30 second increments, stirring after each and repeat until smooth. Once most of the chocolate is melted, stir to melt remaining chunks. It usually takes only 1-1/2 minutes.
Remove truffles from refrigerator and, using a teaspoon, lower each ball into melted chocolate carefully, roll around with spoon to coat completely, then return to waxed paper-lined cookie sheet. Sprinkle with colorful sprinkles to match the Christmas season. Coat half of the truffles with the dark chocolate then repeat with white chocolate.
Store in tightly covered container in the refrigerator. Keeps for 1 to 1-1/2 weeks.