Hi HVHC,
The changing opacity of the header settings is not currently available, but we will make sure to add a customize in the next version. For now you can use the following custom CSS to change the heading color
.lavish_head {
background-color: rgba(255,255,255,0.4) !important;
}
Note: You need to input the color as shown in the above code which you can generate from this link http://css3generator.com/, select the rgba and select the color combination that you want.
Thanks