Image I used (assetid = rbxassetid://280784738):
SliceCenter = 8,8,56,56
Closer look:
If that blending is not a bug and is intended, then the NineSlice feature is a lot less useful than it could be. This means that you can only use NineSlices for items that are the same resolution as the uploaded image. I wouldn’t be able to use it for something like this:
The window’s horizontal size can change depending on the size of the screen, and all of those buttons scale with the window. I wouldn’t be able to use NineSlice for it because oops image is no longer at uploaded resolution and it’s stretching instead of slicing now. So regardless of if this is a bug or intentional behavior, please fix/change it.