Just been looking around and found some interesting customisations of the Grassland theme:
http://www.umlv.net/blog2/ - totally unexpected look with oranges and blue
http://lyon-sauvage.com/ - not really a massive development, but hey :o)
http://www.unautrejour.fr/blog/ - I believe this is in Mali, where these are popular colours - doesn't work well with Western eyes, but that's not the point
http://les5roues2lamain.gazaniol.fr/ - very interesting treatment of the header
One thing you'll notice is that they're all French language sites. Similarly, Anvil was most popular in Russia. It shows how key nodes influence a theme's popularity...