I found these two yesterday in a park, pretending to be leaves. (They were, I wasn't.)
They are called common brimstone (Gonepteryx rhamni), citroenvlinder in Dutch:
I prefer to shoot these against a purple background, but you don't always have that choice.
Here are some older photos of this species:
They don't have the spectacular patterns these have, but I think they are quite pretty in their own way.
Thanks for watching!