@tuanphan hey there, having a similar issue to OP but unsure how to fix.
URL: hikingmyfeelings.org
When I'm on a page that's nestled within a drop-down menu, that particular drop down whites out the box and you can't read the links. Since our programs and offerings have their own branding/coloring, I'm not sure how to fix on each page.
When I'm on our Blog page and hover over Community folder:
When I hover over other folders on navigation:
From our Blaze Your Own Trail to Self-Love page (under programs):
When I hover other other folders from that page:
Is it a matter of doing the custom code on each page header and matching the colors to the branding for that particular page? If so, could you provide that code and I can swap out the HEX codes?