Yes — that is what the token block at the top of theme.css is for. Change the values there and buttons, links, borders, focus rings and hover states all follow. You should not need to touch anything below it.
Two columns, mirrored
This page has a right-hand column and no sidebar — the reverse of the About page. That is three layouts demonstrated across four pages, and none of them required a class to say which.
A form
Form controls are styled to match the rest of the theme, including focus states, which most themes forget. Try tabbing through this one with the keyboard.
Frequently asked
Can I change the colours?
▾Does it need a build step?
▾No. It is one stylesheet and one small script. There is nothing to compile, no package manager, and nothing to keep up to date. Open the HTML in a browser and it works.
What about accessibility?
▾Menus and collapsible sections work from the keyboard, announce their state to screen readers, and close on Escape. Focus is visible throughout. That is a floor rather than a certification — test your own build, particularly your colour choices.