Hey Christopher,
Thanks for reaching out!
I just confirm that there’s no option to change the button background color of the mini cart element. In order for us to change the button background, we need to do it via element CSS using custom code. To do that, please go to Mini Cart > Customize > Element CSS and add this code.
$el .x-anchor{
background-color: #BC3113 !important;
}
To know how to get the hex code, please refer to this article.
Please note that custom CSS code is outside the scope of our support. Issues that might arise from the use of custom CSS code and further enhancements should be directed to a third-party developer or you can avail One where we can answer questions outside of the features of our theme.
On the other hand, I will report this as a bug so that it will be implemented in the future.
Hope that helps.