Do you prefer limes or lemons?
I think it is too much green on top...I would switch to a white overlay to balance things out.
You are getting lots of various responses....each different. I don't think that it's too much green. What I think is that it's too much purple. I would go with: ~ white tablecloths and white napkins ~ purple overlays ~ green apples in vase as the centerpiece I think that would look beautiful!
Switch to lime green tablecloths with purple overlays. Then the apples will be a beautiful contrast to the purple.
I have to agree with some other responses being said that lime green and purple are very bold colors and with the granny smith apples on the bright lime green it can create a brain headache because of too much bold colors. Like someone else suggested a base color is necessary to be the background for the colors, sort of like a painting, so a plain white tablecloth could be like the blank canvas and a purple overlay then with the granny smith apples and your floral arrangement. Just remember to treat your reception like a blank canvas; fill it in with subtle, simple details about who both of you are as a couple.
