In an interview not long ago, James Stewart Jr., a rookie in the professional ranks of motocross racing, was asked about his decision to incorporate bright pink colors into his riding equipment. He said the pink was different and helped him stand out on the track. As if he needed that. The 16-year-old from Haines City, Fla., has stood out for years, and that has not changed in his first year in the pro ranks of the American Motorcyclist Association's motocross series. Motocross is racing on lightweight motorcycles over a cross-country course with obstacles. On his rise through amateur motocross...