Hi Gertrud…thank you for your comment about the theme.
Changing the opacity (the transparency) unfortunately cannot be done easily from the WordPress customizer, however, there is a way to make this change you are wanting.
First, you will need to create a custom stylesheet so that we can override the theme’s own styling. For this we will need a plugin like Simple Custom CSS to do this easily. In this new stylesheet, lets tackle the overall header part that is transparent which is done from this:
#banner-overlay {
position: absolute;
width: 100%;
background-color: rgba(0,0,0,0.23);
z-index: 999;
}
So to override this, we only need to copy this:
#banner-overlay {
background-color: rgba(0,0,0,0.23);
}
Change the 0.23 that you see above to something higher, from 0-1. For example, you can go halfway as 0.50
That part of 4 sections separated by commas is for the transparency level where 0 is the 100% transparency and 1.0 would be solid colour.
We need to do this also for the submenu which will be done in a similar way, except it has a bit more code to it:
@media (min-width: 992px) {
.main-navigation ul ul {
background-color: rgba(0,0,0,0.30);
}
}
By the way, very nice colour scheme you are using…it gives a lighter look and style.