Probably you're talking about this particular problem: ain't that the track turns orange colored, it's just that it together with the player car get invisible, and what's visible are only the sky and the ambient fog, in this case orange because of the selected time of day and weather combination.
It's a fault of the game about default cities and add-on tracks, where when you play SF or London cities and then quit in the game menu to start a new gameplay in an add-on track, happens this; sometimes the game can directly get a crash to desktop with error message instead. There isn't a solution to fix this, the only tip is to exit from the game, restart it and go to play the add-on track. Just remember this: don't play an add-on track right after have played a default city, at least do the contrary.
eh some track of midtown madness 2 got messed up: