Check out the accompanying tutorial here and learn how to convert any shape into printable model:
Most printers support the M600 command, which allows you to change the filament during printing. You can thus use different colours for different layers, creating an illusion of multi coloured printing.
Prusa is offering a free online tool (also available for download) that will insert the M600 command in your gcode files. All you have to do is select the height (layer) at which the filament should change.
This cover test will enable you to see how different colour combinations work together. You can create shades of the same filament by placing either dark or light colour beneath. With this test, you can see exactly how that will look and how many layers are needed if you want to prevent the bottom colour from showing through.
Slice this with 0,2mm layer height. Then, upload the gcode and set the filament-change height at 0,6mm.
When the print reaches that point, it will pause and you can then change the filament.
The bottom plate (first colour) is 2 layers thick. It then builds 1, 2 and 3 layers on top of that respectively.