There's no "cold" side of the switch. The Switch interrupts the "hot" wire. This hot wire comes from the right side to the box and connects to the switch. If the switch is off, it doesn't go any further. If the switch is on, the hot wire "continues" to the yellow caps, and then is split between two wires which you can see in the box on the left. Whatever is connected to these wires is controlled by the switch. Anything that is not controlled to the switch is not connected to these two wires.