How do I turn the graphics screen boarder off in Extended Color BASIC?

[DistantStar001]

I've been taking an online class, and since everyone else has set up their little backgrounds, I decided to put some of my vintage computers in mine running some looping BASIC programs on a green phosphor CRT. Obviously, since the classes run for a few hours, I don't want anything too static (screen burn, also boring), so I "translated" a little dancing line program the 8-Bit Guy had in one of his videos for several of my computers, including The CoCo in extended BASIC. However, the graphics screen has a green border which will be problematic, and I was wondering if there was a command that could turn that off (or at least make it black).

OK. There's also a screensaver mode that needs to be turned off too.

 

[Eudimorphodon]

If it’s a Coco 1 or 2 the border colors are very much set in stone.