You can set the default colors for your text, links, and text hovers in the advanced options of Semplice. Just navigate to Customize > Advanced, and up top under 'Text Colors' you will see options to set default colors.
These colors will be the default colors set for all page headers and paragraphs, unless you've specified something else in the text editor (in which case the default will be override).
If you wish to set default text sizes and customize typography, you can learn how to do so here.