The Vans factory in Orange is a colorful sea of sneakers. The factory's 2,000 workers stitch up 4.5 million pairs a year, of which about 40% involve custom orders. Despite the complexity of shoemaking, the company's mass production techniques have cut the actual direct labor time to make a pair of sneakers to about 35 minutes. "The key to our factory is that we have a very skilled and special work force," said company President Richard Leeuwenberg. Founded in 1966 as the Van Doren Rubber Co., the manufacturer recently raised $43 million in its first offering of stock to the public. Demand has been so strong for the distinctive, rubber-soled footwear--which made Vans famous in the 1982 movie "Fast Times at Ridgemont High"--that the company plans to build a second factory within two years.