Besides using the already available default and gray themes, with the release v5.5.8 (March 26, 2020) we added an option for our customers to create a custom theme for WProofreader. You will be able to overwrite the default styles and adjust the look and feel of WProofreader to the style of your product.
1. Add theme option to the config and specify custom as a value.
2. Create you custom CSS styles to overwrite the default theme of WProofreader.