On a file, when set a pixel to rgba(88,101,242,127), once exported as png it is rendered as rgba(88,100,243,127).
Unfortunately you’ve likely hit a rounding error related to how pixels are stored and multiplied. It’s not unique to PixiEditor, if you try other apps you’ll likely fall into the same issue (at least with default settings).
I don’t have a good solution to that just yet