[graph-tool] Graph drawing: overlay possible?

Hi! I was wondering if it is possible to overlay two drawings of the same graph where I use different color-coded vertex sizes? Theses colors would need to be transparent and the graph layout must match in each drawing. Is there an easy way of doing so with graph-tool? Thanks! Regards, -- Sebastian Weber Group of Cell Communication and Control Freiburg Institute for Advanced Studies - FRIAS School of Life Sciences - LIFENET Albert-Ludwigs-Universität Freiburg Albertstr. 19 79104 Freiburg T.: +49-761-203-97237 Fax:+49-761-203-97334