To prepare crust, combine graham cracker crumbs and sugar in a bowl. Melt butter and stir thoroughly into crumb mixture.
Lightly grease a 9-inch springform pan with butter. Press crumbs into bottom of the springform pan, working them up the sides if desired (a 1-cup measuring cup works well for this).
Bake crust at 325 degrees for 15-20 minutes. Cool completely.*.
Begin making the cheesecake filling by placing softened cream cheese into a large bowl. Mix sugar and corn starch in a bowl and then add to cream cheese; stir until smooth. (You can also use an electric mixer on the lowest speed, but doing so will add extra air into the cheesecake and increase the chance of cracking during baking.).
Crack 4 eggs into a bowl; add eggs one at a time to the filling mixture and stir, scaping down the sides after adding each egg.
Mix in sour cream.
Place two cups of cream cheese mixture into a second bowl.
In the original bowl, stir in vanilla and set aside.**.
In the second bowl, add 2 egg yolks, orange extract, orange zest, and the food colorings, and stir.
Using a 1-cup measure, pour mixtures into the center of the springform pan by alternating white and orange filling. (To create a "perfect" swirl, pour batter directly into the middle of the pan. Each additional pouring will form a new circle inside the last.).
If desired: When finished pouring fillings into the pan, very slightly swirl the top of the cake with a knife to achieve a gentle marbling effect.
Place into preheated oven (325 degrees) and bake for 80-90 minutes or until almost set. Sides should be set with a slight rippling effect at the center of the cake (the cake will completely set as it cools and is refrigerated).
Remove from oven and place on a cooling rack. After about 30-60 minutes you can remove the outside of the springform; you may need to run a knife around the edge of the cheese cake to loosen the sides before removing the springform.
After cooled, place uncovered cheesecake in the refrigerator for 6 hours or overnight before serving. Slice into 12-16 slices.