Preheat oven according to box directions. Spray 9x13 pan with cooking spray.
Beat cake mix, diet soda and egg whites in a large bowl for 2 minutes. Add coloring if desired to make it more orange. Pour mixture into pan.
Decrease cooking time by 5 minutes from what the box says. A toothpick inserted in the middle of the cake will come out clean when it is finished.
Make cake pop batter by mixing the cake and frosting in a stand mixer with the paddle attachment until smooth. Measure out one tablespoon sized balls and
roll smooth. Place on a wax paper covered cookie sheet and put into the fridge to harden a bit.
Melt some of one of the candy bars or candy melts in the microwave. If using candy bars, use the melting directions on the inside of the wrapper and melt into a mug. If using candy melts, put into a microwaveable mug and heat for 45 seconds on high; stir and heat for 30 seconds at 70% power; stir and let sit for 5 minutes to allow the heat of the bowl to continue melting the candy. Stir until smooth.
Take the cake balls from the fridge and dip the stick into the melted white chocolate and then insert halfway into the cake pop ball. After all the cake balls have sticks, stick back in the fridge until hardened a bit more.
After the cake pops have hardened a bit, take out of the fridge. Melt more white chocolate in the same mug. Take the stick and dip the cake ball into the chocolate (I found that if you tilt the mug at a 45 degree angle, it seemed work best for me). Tap off the excess and decide if you want the stick up or down for display. Finish all the cake pops. Add fun sprinkles while the chocolate is wet.
This might sound weird, but I took a shoe box with a lid on it and cut some small holes into the top of the lid. Each time I was finished with a cake pop, I stuck the stick into one of the holes to set. When dry, serve or share and enjoy!