Female species, the inner colour of the forewings are lightgreen-white. The Male has a pure yellow colour.

It is extremely difficult to determine the Colias genus on photos alone. I guess its C. croceus, but it could be the C. hyale or the C. erate as well. Most of the obvious characteristics are seen on the upperside of the wings, but mostly the butterflies are sitting with their wings closed, so that you can't see the upperside.