What are the steps to create a theme or change the existing theme?

[mariobehling]

The site has a basic style already. How can this style be changed now?

[yukiisbored]

The theme/styling is not configured in this repository, but it's configured in the project's repository. This repository just store aggregated HTML pages from other projects.

[mariobehling]

The theme/styling is not configured in this repository, but it's configured in the project's repository.

Where is it stored? Can we store it instead here?

The current way means, if we have numerous repositories of a project and want to change the styling, we need to change it in each repository and ensure it is all up to date. Seems like another reason to move a script and style?