Using custom CSS you can change color of menu bar and menu items from default colors.

For example to change menu bar after scroll down, from transparent black to transparent white with black menu items, please use following code inside custom.css file (more):

.has-sub-image #sp-header.menu-fixed, 
.has-slideshow #sp-header.menu-fixed, 
#sp-header.menu-fixed {
    background-color: rgba(255, 255, 255, 0.8) !important;
    box-shadow: 0 3px 3px rgba(0, 0, 0, 0.05);
}

header.menu-fixed .sp-megamenu-parent > li > a { color: black !important;}
header.menu-fixed .macro-top-search .icon-top-wrapper { color: black; }