The styling within the iframe is standard and set by Shoppable except for the accent color of the buttons which your Customer Success Manager can help you change.
In order to ensure shopper's data stays protected, Shoppable is a PCI-DSS compliant company and handles the checkout page and the order data. This means that if you are using Shoppabl'es Hosted Multi-Retailer Checkout, you will have to place an iframe on your site. You will be in control of the styling on the top of the iframed checkout and the bottom of it.
We highly suggest you keep the rest of the check extremely simple and remove other links so you keep the shopper focused on completing their order. Please see an example below. Our recommendation is to only have your logo on the top of the page.
The styling within the iframe is standard and set by Shoppable except for the accent color of the buttons. The accent color can be matched to your brand color. In order to change this, please contact your Customer Success Manager and provide them with your Hex Color Code.