A new Plone product was released a few days ago, CSS Manager.  Dangerous .. Plone (the backend of this website) does make some customisations quite hard (the learning curve is steep ..), but this new product makes many skin changes easy.  Maybe too easy!  I'm having fun playing with the site colours.  Please don't be alarmed, hopefully the novelty will wear off soon and I'll settle on something not too unpleasant, and roughly aboc-ish (yellow, blue and silver/grey).