Under Tool -> option -> 'fonts' tab, we can set all sorts of fonts.
BUT, to set a different font for each visualization, you need to set the font as its property dialog for each visualization.
And even if you want to apply the fonts you set up in some visualizations equally to different visualizations, you will have to set them manually because spotfire does not know that font settings.
So, I think it is better to make font scheme or 'format painter' function.