RedCheap products can be easily customized using Bootstrap 3 components and styles. In case you want to modify the CSS that are applied by default, then customize them inside the /assets/css/custom.css file. Doing this will include the file after styles.css, which will allow you to override the CSS defined within it. Moreover, it won’t be affected in future when you apply updates to WHMCS software.
It is strongly recommended to add your custom CSS rules to custom.css file rather than editing the provided css files directly.