You can create a custom theme by going to My Pages -> Themes. There, you can choose from a wide range of fonts, and set page and text colours. Once you’ve created your theme, apply it to a particular page by editing the page, going to the Choose Theme tab, and selecting your new theme. Don’t forget to save your changes.
Even within a given theme, it’s possible to change font and font colour in a text box. Highlight your text and then choose one of the Font Family options. There are the usual web fonts and some others. While the text is highlighted, you can also change the font colour using the ‘A’ icon in the text box toolbar.
You can’t change the style of the header text (title) of a text box but you can delete it completely and use the body text as a title. So for example, you use one text box to create a title with a custom font, then another text box for the body text below.
Here’s an example: