@kakrebs: Go to => Appearance => Customize => Additional CSS and add the following CSS Code.
/* To change opacity of background color of text in slider */
#main-slider .entry-content {
background-color:rgba(255, 255, 255, 0.6);
}
#main-slider .entry-content:hover {
background-color:rgba(255, 255, 255, 0.9);
}
You can change the opacity according to your choice.
You cannot make the text area transparent in mobile view as there is nothing behind the area. You can change the background color though.
Let me know if this helps you out!
Kind Regards,
Skandha