Using the block editor, when creating a new page/post, the Title border was previously grey.

Using the block editor, when creating a new page/post, the Title border is now blue.
Create a new post/page. Notice the blue box around the Title.
iPad:

iPhone:

I have looked into this issue in WPAndroid and although I didn't get anywhere concrete, my findings so far may be of help.
I am fairly certain that these are added from the Gutenberg codebase, so it's probably best to get someone from the Gutenberg mobile team to have a look at it. They'd have more knowledge about how to debug things in React native and have the necessary tool setup.
Hope this helps!
I asked @iamthomasbishop about this and here's what I found:
Short version: that’s the expected style because of a change in border-color 😀
Long version: We switched to use stronger borders while working on some of the nested blocks work, but I also just proposed a refinement to how we highlight selected blocks. I am also considering a slightly weaker border color, but I’d like to give it some time because I think it’s mostly noticeable because we’re used to seeing a very dim gray border.
Based on that feedback, I am closing this issue as works-as-expected. Thank you @ScoutHarris for raising the issue and @oguzkocer for looking into it and @iamthomasbishop for the design decsion explanation!
Most helpful comment
I asked @iamthomasbishop about this and here's what I found:
Based on that feedback, I am closing this issue as works-as-expected. Thank you @ScoutHarris for raising the issue and @oguzkocer for looking into it and @iamthomasbishop for the design decsion explanation!