Random change of color or attributes
I was able to reproduce this with holidays and slogans if I cut/paste from Word or QuarkXPress to the Holidays Manager, or Slogans Manager. Some of them were cut/pasted with a carriage return (which holds the attributes) and the rich-text control of the holidays manager dutifully recorded these attributes ... in particular the "black" color.
To remove these unintended attributes, go to the holidays manager, select that holidays set, and from the [More ...] dropdown button, select BATCH and then ALL PLAIN. This will remove all the "black" attributes that are on some of these holidays.