Transparent PNG's have a grey border?

Ahaha, I probably goes too deeply technical on it. Too much info.

Yeah, just keep on experimenting and play around with it.
Developing games is pretty much like playing an adventure game trying to solve puzzles and riddles.
There's always a workaround, and more than one way to solve it.
Last resort, you can always alter the underlying code and bend it to your own rules.

So, the assumption was that this was at it's root a OpenFL bug, but I just dled the latest Stencyl prerelease build (8459) which should have updated OpenFL (- Updated packaged haxe, haxelib, openfl, lime, hxcpp to latest versions.) but I'm still getting this issue if I use scale to fit (fullscreen)...

AFAIK we're using OpenFL's legacy mode which uses some but not all of OpenFL's new code, and we can't switch until the new code is more stable and has the features Stencyl needs (I don't think it supports extensions yet).  According to this post on openfl.org, the problem is fixed in OpenFL "next" which probably isn't included in legacy mode.

I experimented with running a game in "next." I was able to get it to compile but it crashed right away. I'll probably look into it again in the coming weeks, but yeah, we're not at the point where we can transition just yet.

I see, thanks for the explaination.

Grrrr, just noticed, even when I use "Scale Mode" set to "Full Screen", the issue still appears in iPhone 6+ for some reason...

I did upload the images only at x2 scale, but it works fine on my iPad Air so the x4 images doesn't have any issues. Why would x3 have issues? Is "Scale Mode" -> "Full Screen" somehow still scaling images? cause that's what causes it...

Do you want to try using my image to see if my transparency has the same problem?

I used Adobe Illustrator. Then I rasterize the image before exporting.

Pls pardon the small lighter blue squares. It's meant to blend in with a blue background.