Well Enmos, it seems that their is no reference on the internet, would I would advise if you have a interest is to find a book on dermitology and skin disorders, the most comprehensive ones are at Universities.
Bluishgreen skin is occurs most frequently in asia, south asia and india as well the yellow pigmentation of the skin. There may be less documentation with western skin experts so you may have to look at a more exstenive book. As i vaguely remember their are more than one cause for the bluishgreen skin complextion.
Extremely black skin occurs in almost every group of humans, but you find seriously black people in africa.
Extremely White(blanc) skin pigmentaion is found more common that the others and as well in all groups of humans. you can quite frequent documentation on this occurance in Western Documentation, its common name is vitiligo ( Printed in even old books).
Red skin pigmentaion is also another well known, it called Port wine, this condition when prominate makes the skin look purple (purple skin).
Any one of the various skin pigment conditions could cover the whole body to part of the body, or exist as a birth mark.
I agree that it would be nice to have documentation on the occurance of bluishgreen skin on the internet to show as a example and gain insight. But i guess you really have to know what words to type in the search engine to get a list you want. International access would be nice as well.
DwayneD.L.Rabon