The different white and black sides of the Marker are there to remind people which cars are yet to be activated, and is very useful as it is easy to forget when you are analyzing what is the best card play.
Why remind me? At the time someone receives the First Player Marker all cars have to be activated anyways as it happens after the action phase. What do I need a First Player Marker to remind me of that? I still don´t get it...
The marker remains flipped for the whole turn. After about half the cars have moved people can get confused which cars have been activated. At that point you can look at the first player marker and see whether black or white cars still have to be activated.
Ah, now I get it. We always flipped back all cars on the white side after a turn. But instead of doing that the First Player marker tells you, which side will be the non activated side from the beginning of the new turn. Is that right?