Right click the button and choose "Save link as" if it opens in your browser instead of downloading.
Move WD4DAN-NIGHT-COLOR.aclr into your Documents\Affirmatech\N3FJP Software\Shared\ folder.
In N3FJP, click Settings → Appearance → Colors and Fonts...
Click Load Settings and select the WD4DAN-NIGHT-COLOR.aclr file.
Click Done. The night theme is now active.
Click Settings → Appearance → Reset Colors to Light Theme
Click Settings → Appearance → Reset Colors to Dark Theme