Why are the White Sox wearing red today?

Answer 1

The Red Sox wear the standard Home/Away uniforms as well as an additional alternate uniform. The third uniform is sparsely worn however typically these uniforms exist to generate additional revenues for the team. This practice is prevelant throughout professional sports.

Answer 2

Lance Armstrong is at Fenway Park. The players are wearing the bands for the Lance Armstrong Live Strong foundation. Armstrong is running the Marathon, here's the story from Boston Magazine

Answer 3

They are throwbacks from the Allen era. They wear them when they play on sundays