^If not to find creative new uses for pieces, then what is Lego for? :-)

I had this one. Lego had made various racing teams for the Racers theme, and across the sets of that era you can see teams like HOT (which had a yellow and orange color scheme), Maverick (which had green and lime green), etc. Nitro was the "hero" team, inasmuch as they were the team of the main character in the Legoland short film, and clearly meant as one of the good guys among the named characters. However, they didn't stay too focused when it came to keeping the Nitro color schemes cohesive. If you look a the "Nitro Race Team" tag in the database, you'll see that while they are generally blue (often with medium blue as a secondary color) there were strange forays into Lime Green (4589) and the orange/pearl dark grey in this set.

As for the build, it was good, but not outstanding. The truck cab and the hot rod roof felt a little hollow. One novel feature (if I'm remembering it correctly) was that the pullback motor was designed for easy removal so it could be placed in either the hot rod or the semi truck cab. As one might guess, the 6 pullback motor was the most powerful of the series up to this point. It had a lot of torque and was a lot faster than the rest. It coupled really nicely with those big rear wheels on the hot rod. It was also the only purely Technic style motor of the six. 1-3 were System only, 4 and 5 were System with some Technic connector holes.

As far as the Technic Racers went, I preferred the designs of the Slammer Raptor, the Slammer Rhino, and the motorcycles.

Re. Nitro's colour scheme, as mentioned by @brickwright: according to the tie-in comics, Max Axel - the main protagonist of the comics, the Legoland film, and the video game - was originally the driver for a different, otherwise unreferenced race team. In the first race of the season, his car got wrecked, though he didn't get hurt... which was the exact opposite of Nitro's driver, who got injured in a collision during the same race, but otherwise kept his car intact. The two teams amalgamated right there on the spot so they could remain in the championship, with the Nitro team name being preserved, and Axel becoming their driver.

Where I'm going with this... in the comics, the Nitro colours was the blue-themed ones, while Axel's previous team colours were the orange; hence, I think, why both colour schemes appear on Nitro sets. The video game, too, defaulted to the orange colour scheme for Nitro - although that was ultimately subject to player choice.

I... could not tell you where the lime green came from for that other Nitro set, though.