I thoght as far as accuracy of the track, didn't turn 10 tout how they went and measured each track carefully with GPS instruments to get it just right?
As for the extremes of color, HDR is something that is being used more lately to give things a more realistic (less cartoony) look. It used to be that all shades were kept in the normal spectrum and so you never really had any crushed blacks or blown out whites... well it turns out crushed blacks and blown out whites are actually realistic.
And HDRi is usually what's used in good raytracing as it captures dynamic range beyound a normal exposure.
Forza 3 will be implimenting an HDR effect (most noteable when something bright blows out or something dark is completely lost in shadow) while Forza 2 didn't, so keep that in mind while looking at these forza 2 track shows.
That said, looking at the comparisons (at this size anyway) I am actually quite impressed with how well Forza2 shots hold up...