Red Is for Running (for Office) -- at Least, for These VT Candidates

We have two books available right now on or by current political candidates -- Bill "Spaceman" Lee is a noted Red Sox ballplayer, retired, who's entered the Vermont governor's race, and of course, technically, Bernie Sanders is still a candidate for U.S. President. Wonder whether the color choice is coincidence, or the must-have color for such items?? (note: each is signed by its author -- so there's no Sanders signature here ... alas.)