Hi. A few years ago, before Polar Lights sold out to RC2 and temporarily disappeared, it did "chase" versions of its kits. Not all of them, I don't remember exactly when it started. The way it worked, basically, is that something like 1 in 12 of the kits they manufactured would be in a different color of plastic than the rest of the run. Might have been 1 in 10, I'm sure someone else here remembers for sure.
At first, the "chase" kits were all cast in white plastic. I think the Batcycle was that way, maybe all of the Batman vehicle kits. The chase version of the 16-inch Godzilla was in white plastic. As I recall, people started referring to them as "white lightning" kits.
After a while, though, PL started casting the chase versions in different colors. In fact, I think the chase versions of the kits were usually in a color of plastic that made more sense for the kit while the rest of the run was done in white. The chase version of the Hulk was in green, Spider-Man was red, Captain America was blue. The chase version of the 1/350 Enterprise was a sort of creamy color.
I know someone here has done a great job of documenting all this.
For what it's worth, I haven't noticed that these chase kits command prices much if any higher than the regular ones, but I suspect that will change as time goes on and all the kits grow scarcer.