Generally, you should avoid using the Font, Size and Color pickers. They are included in the editor as a convenience, but using CSS styles is a far superior method to getting the right formatting in your pages.

Adding your own CSS is a bit more work, but then all of the style information is in the CSS file, instead of scattered through all of your pages. Later, when you want to change the look of your Screenbook, you can edit just the CSS file, instead of multiple pages.