By default, this module loads the original klaro styles. If you want to apply custom styles, you can advise silverstripe to not load klaro by adding:
---
Name: my-silverstripe-klaro
After: silverstripe-klaro
---
SilverStripe\CMS\Controllers\ContentController:
load_klaro_css: false
You can now include any other css styles you want or build the klaro style from scratch using sass.