When Marlon stocks the vending machine, the camera (inside the back of the machine) shows him stocking the 1st row with brown-wrapper candy bars. He starts stocking the 2nd row with yellow-wrapper bars; Truman interrupts him for a minute (during which Marlon doesn't touch the bars at all). When Marlon continues, the yellow bars have changed to something darker (it's not just a different camera view; even barcodes are different). After another brief interruption, Marlon continues again, and the yellow bars are back.
The motto on the double archway in the Seahaven town center is UNUS PRO OMNIBUS, OMNES PRO UNO: "One for all, all for one" in Latin, thus fitting the premise of the Truman Show.