Customize transparency on the slider text box

On the Customizr slider, is there a way to darken/adjust the amount of transparency on the text box that surrounds the Title/description/button?

I have a few images that I wanted to use that have a light background and/or are a pretty busy graphic, so the Title/description text is getting washed out even with the semi-transparent background of the default text box.

Not the final images, but gives you the idea:
https://www.autoconnective.com/