Dropdown menu opacity

Hi,

I need to adjust the visibility/opacity of the elements that are supposed to appear together with the slider, how can I do it?

I am attaching a scree shot with comments at this link:
https://wp.me/p7pXAe-BO
also please read a brief explanation below.

The opacity of the menu and dropdown entries make them hardly readable when the are opened over the slider.
I have already changed the property in the new color css file as follow:
In
wp-content/themes/enigma-parallax-child00/new-color.css

.dropdown-menu {
 background-color: #152239;
 opacity: 1; /* it was 0.6 */
}

But that change seems to have effect only when I scroll down from the top of the page (so that the slider starts to move away to the top).

Thanks a lot!
BR
Cristiano