If you are at the top level of the box, i.e. not in any of the Pitch or VoiceModeling effect menus, and are not currently editing the MIDI/UTIL or I/O parameters, rotating the data wheel will send you into preset preview mode.
The effect lights and most of the display will flash to indicate the data that exists in the currently previewed preset. This tells you what you can expect to hear should you chose to load the currently previewed preset.
To do that, simply press the Recall button as you are previewing the preset you would like to load. Pressing any other button in preview mode will return you to the preset you were last editing and everything will stop flashing.
If you instead load the previewed preset, the preset you might have been working on will be lost and you will instead be hearing the effects of the new preset.