However, when I attempt to change the navigation color to a darker one, the text color is still white. Please see the attached screenshot for your reference.

 

Could you please share me your site URL where it’s happening so that i can troubleshoot it?

 

Sorry, I just noticed that the height of the header image got shorter after the removal of the page title and description. How can I adjust the height of the header image?

You can adjust the height by using the below CSS code and changing the value 130 in it.

.sh-titlebar-light .sh-table {
    padding: 130px 0;
}