Hi, Reinar. You could modify the header.php file or override CSS, but I’d actually consider just using my Pratt theme instead. It is very similar to this one but with actually quite a bit of code and CSS to fix the navbar to the top.
As to the site name and description, I’m doing it the standard WordPress way. I really don’t get why they only allow a single color choice for both, but a major goal with my themes is to have them be based specifically on how core WordPress and the included Twenty<something> themes work.
For that, I’d use the built-in Customizer to set the color to what you want the site title. Then use CSS to override the description color. The CSS class for the latter is “site-description”. So something like this should work for you:
.site-description { color: #123456; }
Of course if you have a fixed header nav, like if you use the Pratt theme instead, the site description doesn’t make sense to display (it shows site title and top menu) so its a non-issue.
