Have you tried it in Safari 15? Doesn't seem to take effect.

Using theme-color is indeed a good choice for most web pages, but it looks very strange for web pages that require a full-screen gradient background : (

According to documentation, we can’t send messages from a containing iOS app to web extension’s JavaScript scripts. Then if the user switches the ruleset in the app, how and where to call browser.declarativeNetRequest.updateEnabledRulesets? Thanks!