NTSC is the default video system to check. You can change the video checking to PAL.
In the Tools menu Options Options dialog Rendering panel Video Color Check group, change the setting to PAL.
The sample slot does not automatically update when you change the video system preference. Turn video checking off and back on to see the change.
Note: The Rendering panel also shows options for choosing alternate ways to display illegal pixels. These apply to renderings only, not to the sample slots in the Material Editor.