Hello,
1. Please edit the page with the Elementor page builder, and when you edit the “Container” under the “Style” tab you will be able to change the color: https://postimg.cc/DJNMWNSZ
2. To change the button of the Add to Cart button, please navigate to Theme Settings >> Style and Colors >> Buttons >> Accent buttons and change the “Accent buttons background” color from there as per your requirements: https://postimg.cc/1nDvtz1L
3. To edit the header, please navigate to WoodMart >> Header Builder, Please refer to the documentation here: https://xtemos.com/docs-topic/woodmart-header-builder/
Best Regards,