How to prevent a Qt/GTK app (Calibre) from using colors defined in .Xresources?

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http://unix.stackexchange.com – I have colors defined in .Xresources. They look lovely on urxvt, and utterly ghastly on Calibre. Calibre does not appear to have any way to disable or override those colors, so is there any way I can invoke Calibre that would ignore my color scheme? (HowTos)