How Do I Dynamically Change The WordPress Menu?

You can use the body class to load different CSS for the menu. In WordPress, each page or post inserts a unique class into the body tag. Then you do something like this in your CSS file:

.home .menu {
color: white;
}

.aboutus .menu {
color: black;
}

Of course you’ll need to figure out what your actual classes would be.

The more complex way to do it from a programming way would be to modify your page template so that while editing you can specify a light or dark menu for that page.

Then you could just insert a light or dark class in the body.