On politicians/media wearing a  purple tie - at one time

blue and red make purple 

abcNews

Some suggested that the color purple represents bipartisanship: It's not red or blue but middle-of-the-road. In elections, swing states are often referred to as purple states

http://www.guardian.co.uk/politics/2012/

The purple tie is a phenomenon of modern politics. In both Britain and the US, the traditional red and blue ...party colours are being gradually sidelined by purple. 

Esquire.com

A bit of history: As far back as Roman empire, the rich and powerful would show they were rich and powerful by wearing clothes dyed in Tyrian purple, a shade derived from the expensive and rare boiled shells of the murex sea snail. After the whole decline and fall debacle, the color was taken up by generations of European royalty who’d wear robes in imperial purple.

The Atlantic Wire

Interestingly enough, purple's compromising blend of red and blue is the same reason it was elevated to official Washington's color-of-choice: It conveys objectivity and impartiality.

... But in this election, the news media’s objectivity has also been part of the story, …. So rather than risk the appearance of favoritism by wearing red or blue, the press has gone purple

“Purple is the new neutral,” said Jim Moore, the creative director of GQ, ...