Change Skin Tone of Models on JPG (Z)

We have 5 JPEG images We require you to change the skin tone of the models with out changing the colors in the rest of the image. We require you to change the skin tone to be more brown and dark. We want the models' skin to look African. The images are only body images. No face images will be included. Summary: Make models in the image look African by darkening the skin tone. Deliverables: 5 images with models who have darker skin tone.