Hello,
1. that’s the main theme color you select in 8theme options >> styling >> content >> mian color
anyhow if you want change the color for only on that button you need to use this custom css
.btn-underline:after, .et-tabs-wrapper .tabs-nav li.et-opened:before { background-color: #000 !important; }
2. this is not possible by default. you may need some customization for this. I’ll check with my team and confirm this.
3. Appearance >> widgets >> right side top bar >> 8theme social media link and expand then go to the bottom you can see options for ‘link target’ : http://prntscr.com/fgeuhx















