Add a checkbox to print the events' tags to the Day, Week, and Month print styles, and pass its value through the necessary functions.
The Filofax and Month versions always printed in color, regardless of the "Use Colors" checkbox. Pass a useColors flag along with the categories flag.
QTextDocument::drawContents seems to use the current theme to set its foreground color; when I used Breeze Dark with "Use colors" off, it printd white text on the white background. Put the painter's pen color into a PaintContext.