Colias alfacariensis - Berger's Clouded Yellow
These Pale Clouded Yellows are really difficult to tell from the species that holds the name. A slightly more rounded shape to the wings seems to be the most seperable feature. I don't actually think I have any butterfly photographs of the other species, though several times I have thought I did.
These shots were taken too far south, in France and Spain, to be anything other than Berger's.