I have created a custom header with header builder.
I changed color on the top bar to grey ( i have a green topbar as default).
I create a page and choose the new header for that page, but when I open that page, it first shows the gray color for about 1 second, then it changes to the green color that I have on my default header today.
The first thing you should check is whether caching is affecting your header. Try clearing your WordPress cache and browser cache to ensure you’re seeing the most recent changes.
Try to temporarily disable the cache plugin and check the issue.
If you have any questions feel free to contact us.
Can you please share the page url where you are using the custom header. Also share the wp logins details of your site i will check and give you a possible solution.
There is an issue with the 3rd party plugins. Please deactivate all the 3rd party plugins and activate only theme-required plugins on the site and then check the issue. I am sure your issue will be solved. Then Activate the 3rd party plugins one by one and check which plugin is creating the issue for you.
Otherwise, if the issue still exists then keep the 3rd party plugins deactivated and let me know I will check and give you a possible solution.