Revealing mistake: When we see Dark Helmets' hoverjeep in the desert, watch the front end: you can clearly make out the edge of the mirrored box they used for the "hover" effect.
Character mistake: During the scene in the diner, there is a sign that reads "EMPLOYEE'S ONLY." There shouldn't be an apostrophe.
Answer: Its a reference to how the stars streak around the ships in "Star Wars". "Ludicrous speed" had to have a ludicrous color. It is also referencing 2001: A Space Odyssey, where this "tartan" effect occurs when Dave is in the pod towards the end of the film.
Grumpy Scot
Those answers are quite correct and possible, but how about this: Warp and weft are the two directions of yarn in weaving (of plaids and other things). It might be a very meta joke since plaid is at much higher level than warp. On the other hand, it's Mel Brooks. On the gripping hand, he was born in Brooklyn in the mid 20's and might have been exposed to the basics and vocabulary of the tailor at a young age.
Btw, it's also a clear reference to the sentence from Star Trek "They've gone to warp."