Gembrace

Hi, I'm new to lua and OpenComputers but have been getting along well enough. However, I would like to use the script provided in this post for a mob farm control system. My problem is that by default the background is white and I can't figure out how to set it to black like I'd prefer. I've done some searching and tried a few ways of changing backgrounds and ended up failing in the end, so if anyone knows how to do this with this script, I'd appreciate it.