What type of relay/switch that would make to lights blink?

I have 2 battery opperated rope lights and I want to make them flash back and forth. They are both 6 volts and 6 feet.

Then set up a 555 timer flashing circuit.Something like this will get you started.

http://www.555-timer-circuits.com/flashing-led.html

Now you can make one setup for each set of lights or you can use a 556 timer which is just 2 555s on the same chip.