We have a Smart App Banner (including App Clip) on our website and have noticed today that the banner's background color has changed. It no longer has the default white background and blue button color, instead it has a background color that matches our page's background, and even the color of the button has changed.
What's interesting is that we have not triggered this change at all. The colors seemingly changed by themselves.
Looking at the Apple Documentation, no customization options are mentioned. Searching the web, the theme-color meta tag is mentioned in relation to this, however we haven't even included that tag on our page.
What is triggering this color change then and how can we influence it?