K-5 green skin tones ?
Was this perchance a night game? Some kinds of gymnasium and outdoor and such lights can produce a distinctly greenish cast. If there's still some natural light, and hence mixed lighting, there isn't much you can do to get all the colors reasonably correct looking.
Otherwise, as others suggested, it might be an accurate rendering of a color cast from light reflecting off the grass.
(This is one area where shooting in RAW or in RAW+JPEG is helpful; if you get a color cast from a mistaken white balance or whatever, you can much more easily and accurately correct it afterwards.)