You can change the font type, style, colour and size of the price field. This fields can have differerent sytles in list view, detail page view and also on the home page. If you change text sizes in the website just make sure that you check after the change to see if they still fit OK in the website.
To change price size and colour - Go to Design menu >> Advanced design >> Click in to the main content area – This selects the content area to be changed and also will change the ribbon menu.
The Ribbon menu at the top will change and you select Prices and product views from the Preview drop down menu.