This is not really an effect (in the sense that I don't think it was wanted). This is more an (unwanted) artifact called "banding".
What likely happened here is that the thighs and elbow were in the shadow and considered too dark, so their brightness was increased. Unfortunately when you start with an 8-bit image, the range of values isn't very wide and if you map this narrow range (say, 10-20) to a wider range (say, 40-60) you get gaps, because all pixels with the same original value get the same transformed value: all the pixels at 10 goes become 40, those at 11 become 42, etc.. and those at 20 becomes 60 and there are no pixels with an odd value. In the picture this translates into color jumps between rather different values, to which our eyes are very sensitive when they are aligned and see them as color bands. To make matter worse this was probably done in RGB space so the stretch isn't the same in all three colors channels and induced a color shift so the slightly higher red of the flesh tone became the much higher red of a bruise.