Spray some light gray primer on it and repaint the skin (face and hands) by a coat of correct skin tone (by using airbrush) than complete the details as you want them to be by using fine brush and correct paints.
However if I were you and if I had a chance, I'd just return it..without getting into trouble of painting
Eyebrows need to be completely painted over and then slightly colored. They are way too bold and dark. Hair color needs to be lighter (dark blond). Skin color needs to be made darker. Eyes need to be changed from the current light blue to a darker blue/green. And finally, a slight 5 o'clock shadow could be added. My mock up is crude, but it looks 100X better.
You might want to check out the "Custom and/or Hand-crafted Products" sub-forum in the Open Market section of onesixthwarriors.com. Typically there are at least a few skilled painters there looking to take on 1/6th-scale head commissions at any given time.