Tie fighters! The wardrobe strikes back!

The first hustings of the campaign (you can see the entirety of the speeches on grainy video).

I have one question - where did Menzies, Simon and Chris get those identikit shiny (blue) ties from? Why blue? And, more importantly, why did Mark Oaten miss out? Was it a group decision or was there one of those uncomfortable 'we're all wearing the same outfit' moments?