ISO itself does not directly change white balance or skin tone color. The more likely cause is that the two frames were not truly identical scenes for the camera’s auto systems.

From the examples, other things changed too: framing, subject posture, and likely the light. One image includes different amounts of skin, greenery, and brick wall, and those scene contents can influence Auto White Balance. If clouds were moving, the mix of direct sun and shade may also have changed, which affects color temperature and skin tones.

In other words, AWB and evaluative metering are analyzing each frame independently. When the composition or light shifts, the camera may choose a different white balance even if your main exposure change was ISO/shutter speed.

If you want consistent color, avoid relying on AWB for critical shots. Set a fixed white balance (such as Daylight, Shade, or a custom WB) and, ideally, shoot RAW so you can fine-tune color later without degrading image quality.