Other mistake: As Dark Helmet says his line "Everybody knows that!", watch the crewman in white to Helmet's right. He starts to cover his crotch a beat too soon.
Other mistake: When Yogurt comes out of his statue the camera zooms in and the door starts to close, but when the camera zooms out the door starts back and closes again.
Other mistake: When Lone Starr drops the statue of Yogurt on Barf's foot, the statue actually lands beside his foot.
Other mistake: When Dark Helmet kills the crew member, he chops straight down the man's right side, but the slash mark shows a right-to-left downward slice.
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."