Border around a parallax-picture

Hi, I’m back again.

The Adam`s plugin runs good, but I got a border around the picture like this

The Backround of my side is in light grey (fcfcfc) and the Adam`s plugin make a border around the picture
in white (ffffff). How can I delete the border? Or make it in fcfcfc, too?
I work with the theme Vantage.

Please help! – many thanks

Yours Fiona