Yes, the widget has custom selectors that you can use to change how it appears and we provide settings within the app where you can add your own custom CSS to target these selectors.
The default styling of the survey widget on the Order Status Page does have very good survey response rates.
We believe tat this is down to the widget blending in well with the natural style of the Shopify post purchase page and appearing to be an integral part of the page, which in turn encourages customers that by answering the questions, the merchant is better placed to understand their needs and preferences.
If you'd still like to make changes to the style of the widget, then please take a look at our article on styling the grapevine survey widget.