The heading text is set to use the Site Title from the General Settings page if you’re not using an image logo.
If you’d like to format the text, I’d suggest using a plugin called Fontific to make those changes for you.
It lets you enter a “selector” and then style the text for it. The select to enter for the site title is this:
#text-logo h1, #text-logo p
Enter it into the spot for the selector in the top left of the plugin screen and you’ll be able to adjust the size, color, font and so on.
If you have any trouble, let me know.