PWA manifest.json - "theme_color" and "background_color" not working, splash screen not showing on android device

"If you page already has a theme-color meta tag — for example <meta name="theme-color" content="#2196F3"> — then the page level configuration will be used instead of the value in the manifest."

from: https://developers.google.com/web/updates/2015/08/using-manifest-to-set-sitewide-theme-color