Are there any CSS classes for the wordpress colours?

No. The only styles that WordPress itself loads on the front-end is /wp-includes/css/dist/block-library/style.min.css, and this stylesheet doesn’t include any such classes or colours. All other styles are the responsibility of the theme.

So if you want to know if a specific theme has such classes you would need to ask the author, however I don’t know any reason why anyone would include the WordPress brand colours in their theme.