During the only televised debate between Ronald Reagan and Jimmy Carter in 1980, each wore a black patterned tie.
In 2008, both Barack Obama and John McCain each sported red ties with white stripes. Clearly, things turned out better for Obama that year, but a red tie certainly leveled out the playing field for McCain.
An outlier has shown up just once since debates were broadcast on color TV when Bob Dole, the Republican challenger to Bill Clinton in 1996, wore a green tie. We all know how that one turned out.