As a new user of QGIS, one of the tasks I frequently perform is creating a layer where polygons are colored by class, classified by some nominal field in the attribute table. I have developed a habit of switching to the old symbology, because it makes this task easy for an arbitrary number of classes and I can re-randomize the colors until I'm happy with the results. I haven't found any way to do the same thing with the new symbology. The closest I've found is to select "categorized" in the new symbology and select a color ramp, which works well for ordinal data but not so much for nominal categories. I presume that such an important function was not lost in the design of the new symbology, but that I've simply been unable to find it in the manual. I'd prefer to work with the new symbology, simply because that's the direction that QGIS development is going. Can someone explain or direct me to appropriate documentation of how to accomplish this? Thanks in advance.
In the new symbology choose Graduated then define a new color ramp, by choosing Color ramp option and going down on the menu. When you define a new color ramp you have the option Random. Then you can make some settings on the number of classes and the colors and then save the color ramp. After you created the random color ramp you can choose the number of classes equal with the number of colors defined on the ramp and click on classify. You can repeat the workflow until you have the desired colors.