VOPlot sports a new look-n-feel (skin). The look-n-feel is made using Synth Look-n-Feel which is bundled. with Java v5.0. For some reason you want to shift to another look-n-feel which you are comfortable with like Motif or Metal you can do so from clicking one of the radio buttons in "Look-n-Feel" menu.
Certain look-n-feel options are dependent on the operating system you are running. For example, GTK Look-n-Feel is available on Linux but not windows. If a look-n-feel is not supported on that system, no option for setting the look-n-feel will be shown in the "Look-n-Feel" menu.