Hazard warning switch wiring
 

Hi there. Have just imported a vette into the UK, a 1975. To make it legal for UK roads, some modifications have had to be made to the lighting. My only problem now is with the hazard warning switch. It doesnt stay in at all. If you press hard, the hazard lamps flash but as soon as you release, they go off. Whilst I will repair it some time soon, I need to get the car back to the garage for its Re-Test.

I have a redundant on/off switch under the dash, possibly from an old alarm system now long gone. I want to wire this in parallel with the existing switch.
What I am trying to find out is which colour cables actually go through the column hazard warning switch. I will just splice into these under the dash to make the hazards operational.

Thanks.