Line an 8x8" pan with wax paper that has been sprayed with cooking spray.
Ina microwave safe bowl, place 1 1/3 cups of white chocolate chips in a microwave safe bowl. Heat in 30 second intervals, stirring in between each intervals until chocolate chips are completely melted and smooth.
Add approximately 1/3 of the frosting into the melted chocolate, along with a few drops of yellow food coloring (until you reach your desired yellow color).
Stir to combine, and adjust the shade to your desired color.
Pour the yellow fudge into the prepared pan and refrigerate until mostly set, about 20 minutes. The fudge does not have to be rock hard, but should be set enough so that it doesn't move when the pan is tilted.
Repeat steps 2 and 3, adding 1/3 of the frosting and orange food coloring (instead of the yellow). Pour the orange colored fudge, smooth it in an even layer, and return to the refrigerator to allow the new layer to set (about 20 minutes).
Repeat steps 2 and 3 one last time using that last of the chocolate chips and frosting, but do not add any food coloring. Pour the white fudge over the orange layer and return to the refrigerator once more and allow it to set fully about 2 hours.
To serve, cut the fudge into 1-inch squares. Be sure to use a large knife with a smooth blade, and wipe the blade frequently to ensure that the sides of the fudge squares do not get smeared with other colors. Store it in an airtight refrigerated container.