Thanks for your question and description. I’m a little confused because I think an image or a screen recording will work better for your description for me personally. Maybe other developers will benefit as well.
Are you using dark mode and seeing the Liquid Glass automatically tries to set the foreground? Double-check your settings for Dark Mode and Automatic switching. Make sure it isn't set to automatically switch based on the time of day. Ensure that the "Appearance" is set to either "Light" or "Dark" and is not set to "Automatic." If it is, adjust the schedule so you know what to expect.
The color shifting and black stripe are not normal but there is a way to adapt to the background, so a screen recording can help developer here understand what you are seeing.
I would recommend this documentation on design principles that has a good explanation of expectations in my modest opinion. But I’m also trying to see if that is normal in Liquid Glass as something is causing the colors to change?
https://developer.apple.com/documentation/TechnologyOverviews/liquid-glass#Design-principles
Oh and check the settings at, top of my head I should double check:
To reduce the transparency effect:
Go to Settings > Accessibility > Display & Text Size.
Turn on the toggle for Reduce Transparency.
Albert Pascual
Worldwide Developer Relations.