@lux 

Use this CSS code: 

#wpforo #wpforo-wrap .wpf-tags a {background-color: #011935;}
#wpforo #wpforo-wrap .wpf-tags a:before{
    border-color: transparent #011935 transparent transparent;
}

@lux 

 And when i do hover in the tooltip tag?

Here is the code you can use: 

#wpforo #wpforo-wrap .wpf-tags a:hover {background-color: #00A59D !important;}
#wpforo #wpforo-wrap .wpf-tags a:before {
border-color: transparent #00A59D transparent transparent !important;
}

The tags in this url:  https://www.institutodelaverdad.com/comunidad/?wpfin=tag&wpfs=QUEUEUM  show a border right: white...

You can remove it using the CSS code below 

#wpforo #wpforo-wrap .wpforo-search-wrap .wpforo-search-content td.wpf-shead-icon {border:none}