Change styling in product options for e-shop

Hi everyone, 

Cannot find a way to change the styling of the drop down menu for the product page on Squarespace 7.1. See example below - I would like to make the outline pill shape and a different colour than black. 

Anyone would know how to or have a CSS code for this? 

Thanks a lot! 
KM

Please post a URL for this product page.

If your site is not public please set up a site-wide password, if you've not already done so. Post the password here.

We can then take a look at your issue.

It is easier to work with your site live than other options.