[quote="Gordon Laing"](off topic: Wow, that Audi looks nice!)
The only filter which you should consider is a circular polarising filter. As these are rotated, you'll see they can make blue skies even bluer, and can also remove reflections from glass and water - but NOT metal.
Polarisers do however require longer exposures, so you have to be careful about camera shake unless it's very bright. And in some conditions they won't make any differecne at all. So don't attach them unless you want or need their effect.
As for those photos, I didn't see anything which would have required a special filter - just nice lighting and careful composition. The headlamp rainbow weffect was probably accidental and was just the way the light was caught in there - although again a polariser could give you more control here.
If you want punchier colours, again, this is something you can do afterwards in software. You're looking for a Saturation control - turn it up and the colours will be boosted.
yes thats what i was looking for
btw i saw a white one of those today..