I ran a bunch of tests using full white for the colors, when set at all. This is the results. The first one, as indicated, is using whatever the default is:
Interestingly, setting the background only to alpha 100 yielded the same results as when both are set to full 255.
It's actually hard to tell but the border color on the third and fifth image are actually the same. Sampling the values shows they are both 100.
The 'color' for the center on the fifth one is 161 instead of 100. And the center of the fourth sample is 255. I suspect that is the affect of adding whatever bleed from the border to the alpha of 100 in the center reaching above 255 (the max).
There is clearly a bleeding issue happening if the background alpha is set to something other than 255. But it does not happen if it is just the border alpha being set.
I suspect a lot of tests were not done to see this kind of interaction.
Since it is not a critical issue, I don't think TGC is going to try to fix it for V1. But, we'll see if it still demonstrates in V2. If it does, then we'll flag it as a bug.
Cheers,
Ancient Lady
AGK Community Tester and AppGameKit Master