How to reference primary color in Radix Themes

Question

const Header = () => {
  return (
    <header className="absolute w-full px-5 py-2">
      <nav>
        <Heading size="5">Level 1</Heading>
        <Button variant="soft">
          <HamburgerMenuIcon />
        </Button>
      </nav>
    </header>
  );
}

when run, this component will be rendered like this,

Note that the background color of the hamburger menu icon button. How can I set the background color of the header to have the same color as the icon button?

In MUI, we can reference the primary color like color="primary". Are there similar variables in Radix Themes?