Silver for me... stays 'clean' looking even when dirty, doesn't attract loads of attention as its not a shouty colour and of course is the colour of the touring car A4's of ye olde BTCC days... and one of the reasons I got into Audi's in the first place
I've never ever seen a Mocha one before! Only available at launch and then immediately discontinued (although the colour has subsequently appeared on other more recent VAG models). Anyone ever seen an Ochre one?
Santorin Blue, Red and Imola Yellow( Yet to see one in person ) are my favorites. Santorin Blue isn't very common but I think it looks incredible. It's the one on the left. Silver is also very smart. Ming blue is just too dark for me, I've heard too many people call it black. Just my two cents.