I see. It works. But now how would I be able to just set the colors for the sticky navigation & header (once they being merged)? I would like to set the background color and text color for the merged sticky navigation & header.
You can use the Customiser > Colors > Primary navigation, this will control the base colors for the nav and the sticky nav.
You can then override the base nav colors in the Page Header Advance tab, so you could have a transparent nav that becomes a solid color on sticky.