Video tutorial

Advanced Search colors can be edited from theme options:

For older theme versions you can modify the button colors with this custom css:

This colors is modified with this css in theme options – design – custom css or child theme style.css (if you activate it from theme pack)

#submit_booking_front, 
#advanced_submit_widget, 
#advanced_submit_2_mobile, 
#advanced_submit_2 {
    margin-top: 0px;
    padding: 13px 15px;
    color: #fff;
    background-color: #4d5567;
    font-size: 16px;
    font-weight: 600;
    width: 100%;
    margin-bottom: 0px;
    border-radius: 2px;
}

#submit_booking_front:hover, 
#advanced_submit_widget:hover, 
#advanced_submit_2_mobile:hover, 
#advanced_submit_2:hover {
    background-color: #576074;
}