Setting dot color in Graph3d 'dot-color' mode

Looking at the documentation in http://visjs.org/docs/graph3d/, I can't see how to set explicitly the dot color of a 3d graph. If in the graph style is dot-color mode, then both dot color and dot size are set by the data in style column. But it is unclear for me, by which formula it is being done, and moreover, when creating a number of simultaneously plotted graphs, I have to sync their legends and so have to be able to set each dot's color explicitly

Thanks,