The Shopify theme "Dawn" has a fixed header background, and cannot be displayed over a slideshow or image banner. Here is an example of how to set up header background transparency using Javascript and CSS. You can also turn it on and off in the theme editor.
An example of how to make the header background transparent on the top page of the "Dawn" theme, allowing it to be displayed over a slideshow or image banner.
[Settings Step 1] Add the scheme to "settings_schema.json" and the label to "ja.schema.json"
[Settings Step 2] Add the scheme to "header.liquid" and the label to "ja.schema.json"
[Settings Step 3] Add two display codes to "header.liquid"
