The interesting thing about this image is that the cast is not uniform. It may not necessarily be a cast, according to the numbers, but the woman's skin tone has a lot more yellow in it compared to magenta in cmyk terms. The man's skin tone is a closer mix of yellow and magenta. There are "recipes" for the cmyk ratios for caucasian skin and, although everyone is different, they give one at least a starting point for judging color. According to the original image posted at the top of the thread, the skin tones for the man are pretty good compared to a "recipe" while the woman's tones are way too yellow, hence the greenish looking appearance. The clouds in the background appear pretty reasonable in terms of neutral-to-blue. If the man is sunburnt (more magenta versus yellow than normal), for example, then my argument sort of goes out the window.
@Michilebaker - do you have any recollection of this difference in skin tone when you took the shot, assuming you took the shot? Just a thought. If the subjects are that different, any white balance technique is not going to "fix" the issue. In this case, where the skin tones are really important, maybe shooting with a reference card in an image will help (either a gray card or a color checker). In this image the skin is the focus of the image, so it is pretty important that it is correct. If the woman's skin is really that "yellow" then you can leave it or take a little creative license and pink it up a bit to suit your vision of the image without completely veering off into make believe - or, you can do whatever you;d like!
Have fun!
Kirk
.
; 
