If you have added any user attributes while importing the .son file, you can use a colormapper to color the nodes according the the values of the attribute. The Graphics Settings dialog (click view settings in the layout window) now has a checkbox named Node Color Mapping in the node options. Clicking the box will bring up the "Edit Color Mapping" dialog. The pop-up menu in the upper left lists the names of variable attached to the nodes. Selecting a variable shows a list of all the values with an arbitrarily assigned color. Clicking any of the colors will show it in the color chooser. You can select a new value and click the "Assign Color" button to modify the mapping.