what wire is used to wire 2 way switches? this has been bugging me for years

in my hall way at the top of the stair case i have a switch that operates the light for the staircase, theres also a switch at the bottom that operates the same light so if you turn it on at the bottom and go up stairs you can turn it off from the top and vica versa.
having looked at wiring diagrams in the past many times to relieve my curiosity on how they are wired i have have long ago figured it out but what i have not yet figured out is what type of wire they use?
is it some special wire that has 3 different active colours and not a green for earth like normal twin and earth wire has? or do people run 2 lots of wires or something for these setups?


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