I edited my post to show the result in different browsers. I noticed its closer on Firefox and the border width is also correct on Firefox, but not an any other browser. I cant publish the app because I don’t have a domain for it yet (and I am on free version as the features are not there for me to pay yet).
App preview in Chrome:
App preview Chrome Incognito:
App preview in Firefox:
App Preview in Edge:
I tried changing my secondary color, which looks like the gray color on the Firefox preview, but the border color still remains gray/black.
Firefox and Edge have no add-ons or anything. They are as they would be if you just installed them. “Stock” browsers, if you will. 