Hi lej,
Thanks for reaching to us and take our apologies for the long delay in answering.
Navigate to WoodMart > Header builder > edit default header (highlighted star icon) or you can go through the admin bar directly https://prnt.sc/Ct9ehRDvvDV9.
Click on Settings
button and disable Make it overlap
option https://prnt.sc/t9tDLt8KWk82 > https://prnt.sc/1p60FbT7tCPP
Click on the settings icon to edit it https://prnt.sc/HuA54fAGqvjm > Style tab > Here you can change the background-color https://prnt.sc/jiJwmWUxnYjm
With that demo, when you scroll down then the sticky header has background color as well. If you want to change the color, please add below Custom CSS code to the Theme Settings > Custom CSS > Global:
.whb-header.whb-sticked .whb-color-light:not(.whb-with-bg){
background-color: #fff;
}
Regards,