Need help: slide border color

Hi everyone, 

I am trying to create an 'invisible' player, so I proceeded matching the player colors with the background.

Everything was ok until I noticed that there are still unmatched elements, specificaly around the slide, as shown in the image below. 

This element does not appear on the color scheme options, and they are not elements of the slide. The line appears only aside and below the slide. 

Does anyone experienced something similar? What can be done to get rid of these lines? 

Thanks!