I may have meant a DPDT switch, which means dual pole, dual throw.
Look at the diagrams below:
You would wire the oem wire to post B (one for each side, there are 6 total posts, keep them seperate to prevent the wrong lights from lighting up.)
Then amber to post A, and blue to post C.
In position one, the posts A and B are connected to close the circuit, and when the turn signals are activated, they will light up amber, flip the switch to position two, and the posts B and C are connected and the signals will light up blue.
You would have to run wire from the kick panels, to the switch, back to each mirror, so you would need to get some extra wire.