No Idea

Did you know that Edinburgh Airport currently has the ability to turn its iconic air traffic control tower different colours?
 
Over the past couple of years, the tower has been lit up a number of different times for various events, including red for Remembrance fortnight, blue for the Scottish Rugby Six Nations, green for St Patricks day (in conjunction with Aer Lingus) and white to support Police Scotland’s white ribbon campaign.
 

I think I must have been sleeping I pass it every day and yet have only seen the purple-wonder what that means?