Hi Carl,
I presume you're seeking help with Australian Aboriginal skin tones??
If so, I think Einion has given you the right mix of colours. In addition to the Vallejo colours mentioned, I would also suggest you do a series of burnt umber oil washes over the acrylics to give the skin some depth and a slight sheen.
Of course there is a great deal of difference between the skin tones of Aboriginal people from the hot inland desert country and the more temperate coastal regions in the south east. Desert people are generally much darker in colour, whereas the southern people tend to slightly lighter in colour (more sepia toned if you understand me).