This is most likely a bug in your video driver that occurs only at certain color settings — for example, it may happen only when your monitor is set to display "High Color".

You can probably fix the problem by switching from High Color to True Color, or vice versa. To do this:

1. Click the Start button
2. Choose Settings
3. Choose Control Panel
4. Open Display
5. Click the Settings tab
6. Choose a different setting in the Colors section
7. Exit and reopen Holiday Lights

For a more permanent solution, you may want to contact the manufacturer of your video card to see if they have an updated video driver that solves the problem.