OH PoppyCock. If they were in fact wearing green and you pinched them, they are warranted to pinch you ten times back!
If not they are asking you to pinch them, feel free, but if the sparks fly invite her to pinch back. When I was attached as a young man, I would wear green. When fully single I would flaunt no green in order to be pinched!
I am now such an old cad, that sometimes I pinch the ladies who are wearing green just so they will pinch me back.
The only thing the wonderful day stands for is happy.