A Friend asked me to post this and see if I could get an answer for her. I've never had this happen but I don't see why it couldn't.
"I have golden egg squash (the yellow kind), and it's been pure yellow, and we have been getting tons! Now the ones that I am getting are still pretty yellow, but they are also getting green splotchy spots on them. It's almost as if they are looking like a zucchini. Is there such a thing as cross pollination? Because I do have them planted VERY close to zucchini. "
The zucchini and the Golden egg squash are both the same species (Cucurbia pepo) so they could cross. (They are actually just different types of zucchini.) BUT the cross only affects the seeds themselves, so the fruit of the Golden squash would not be affected. If your friend saved seeds from her squash, and grew them next year, then the fruit could be a cross. Saving seeds from Golden Egg isn't recommended, though, since it is a hybrid itself. It isn't very likely that the seeds would grow true.
If all the fruit has the green splotches then it may be related to stress, heat, lack of water/too much water, or a shortage of nutrients. Did the change in color coincide with any other know issue? Does it affect the taste at all?
Green splotches usually means a virus, usually cucumber mosaic virus. Yellow type summer squashes are especially vulnerable. The only way to avoid it is to plant a resistant variety that has the precocious yellow gene. It just mars the physical appearance not the edibility. Some yellow zucchini types (One Ball is a good example) will grow green as the the temperature reaches triple digits. http://vegetablemdonline.ppath.cornell.edu/factsheets/Viruses_Cucurbits.htm
Thank you, I'll relay this information back to my friend. I'm trying to get her to join Dave's. So maybe getting some good answers will be an inspiration to do that. I learn new stuff on here everyday!