Hello, @microw007,
1- I was testing your issue by adding a new button on the site. There is no issue, it works just perfectly fine. Please check the video by clicking on the link: https://streamable.com/nropmx You will see it is working perfectly.
Try to check back your issue after clearing the browser cache or in a new browser.
2- In order to know the first button is and how can you edit it please watch this video: https://streamable.com/ehzb5c
3- To edit the color of the product categories simply go to the Dashboard >> XStore >> Theme OPtions >> Theme Custom CSS >> Global and the paste the below code at the bottom of the CSS box there.
.sidebar-widget ul li a, .widget_product_categories.sidebar-widget ul li a{color:black !important;}
Then save settings and check back to your site after clearing the browser cache. Result will be appear like this: https://postimg.cc/t1Qk2jfV
Regards 8Themes Team.