Ok... if all 3 instances are running Pi-hole v6 and all 3 instances show correct colors in a different browser, the issue is definitely in Chrome (for iOS).
I can only imagine 2 possible scenarios:
-
Chrome is using a browser extension or you are using a Chrome option to "force" a fake dark mode, like in this issue: Greyscale Query graph on iPhone?
If that's your case, this is really a browser bug and this is the suggested fix (Turning off the option should also work for Chrome). -
Another possibility is the browser is using an older CSS file (cache issue) for this specific instance. The solution is to clear the browser cache.