Full screen slider text background colour

Hi,

I have a full screen slider and would like to add in a background colour to the slider text captions (large and small text captions).

I’ve looked in support and tried a couple of things that did not work. I did get it to work on the first caption by changing the shortcode.css to read the below but this does not effect the paragraph text, and does show up on mobile and i suspect there is a better selector to use to do this. Any ideas?

.avia_transform .av_slideshow_full.avia-fade-slider .active-slide .avia-caption-title,
.avia_transform .av_fullscreen.avia-fade-slider .active-slide .avia-caption-title
{
background: #000;
filter: alpha(opacity = 80);background: rgba(0, 0, 0, 0.5);
padding: 20px !important;
display: inline-block;
visibility: visible;
-webkit-animation: caption-top 0.5s 1 ease-out;
animation: caption-top 0.5s 1 ease-out;
}