Callophrys rubi Green Hairstreak
I've only taken very poor photos of this butterfly in England which flits quickly from site to site but both in Spain and France they seemed to settle for a bit longer (about 20 seconds) so I got close enough to take a recognisable photo.
LHS: near Mojácar, Spain 19th March 2007 RHS: Ossue valley, French Pyrenees 10th June 2009
Added on 25th June & November 6th 2008, updated 14th April 2010, updated 4th June 2010, updated 12th Nov 2014