To remove Header Color on Scroll, you can use these CSS codes to Website Tools > Custom CSS.
#1. All Pages
header#header.shrink {
background-color: transparent !important;
}
header#header.shrink .header-background-solid {
opacity: 0 !important;
}

#2. One Page
You can find Page ID. Then use CSS code like this.
#collection-6673f2e18432c25013aee99f {
header#header.shrink {
background-color: transparent !important;
}
header#header.shrink .header-background-solid {
opacity: 0 !important;
}}
#3. Desktop Only
@media screen and (min-width:768px) {
header#header.shrink {
background-color: transparent !important;
}
header#header.shrink .header-background-solid {
opacity: 0 !important;
}
}
#4. Mobile Only
@media screen and (max-width:767px) {
header#header.shrink {
background-color: transparent !important;
}
header#header.shrink .header-background-solid {
opacity: 0 !important;
}}