I designed a poster in Adobe Illustrator. On that poster, I used a smudge stick effect on a plain black background from the effect gallery panel. Once I was done, I wanted to export the file as a PNG file. Once I finished saving it, I preview it, and I see this colored border surrounding the artwork. I decided to then remove the smudge stick effect from the black background. Once I saved and exported it, the color border is not there, and I realised this color border only occurs if I use a color background with an effect from the effect gallery. Could anyone explain why this happens? Here is an image for further details. Note that the images look different in terms of the borders and size.