Actually, from my understanding the headlight/grill section is where they usually aim because it is the most reflective and easiest target to hit. and they need the laser to "bounce" back at them. Plus I don't think the colour of the car would effect the laser to any degree. But if it did, red absorbs red, the whiter the surface the more reflected the light is, basic physics. The finish would be a more helpful element, if you had a matt type finish to the car it would make it harder, so when I see those primered stangs with no paint, I think there is something to that?? I work with spectrophotometers/fluorometers all day long and deal with light transmission and reflectance at work and some lasers which by the way operate in the 700ish nm range. If you could pick up a ****load of LED's that emit the correct nm range and put them all in your grill you would absorb the signal and would ultimately defeat the laser. That is what those laser jammers do, but if you could build one yourself it wouldn't cost a grand and you could custom fit it to the most reflective parts of your front and rear for that matter, for photo. So they could try and lock on you all they wanted but would get jack.
Plus I have a friend looking for the red LED's in the correct range at bulk price, which is apparently harder to find then you would think, probably for this reason as normal LED's are off by a bit in the spectrum from the laser guns. Curious??