To add to this, the green that you see is from the offset of primary colors creating the dark patch underneath. Since the magenta is nudged in the positive y direction and the blue is nudged in the negative y direction (and a slight positive x), we get a cool color mixing effect where the dark hues from his hair are present on his neck but it is without the magenta being mixed in. So all we get is the product of strong quantities blue and yellow which is green! Even more apparent due to the situational contrast.