Hi!

I could not see your message here, but if you mean you wanted to set the alpha channel for the background color of the tab elements, please try using this custom CSS:

#root-container .vc_tta-style-theme-default .vc_tta-tabs-list .vc_tta-tab a,
#root-container .vc_tta-style-theme-default .vc_tta-panel-body {
    background: rgba( 0,0,0,0.2 );
}

You can change from "0.2" to any other number (max is 1) to set the value of the transparency.

Regards,
Paul