REQ: add options to scr_conback

[mushis]

Is your feature request related to a problem? Please describe.
no
just a feature request to add more options to scr_conback.
I would like to set a black console background,
which would be just black pixels, no need to render the image, just show black.

Describe the solution you'd like
scr_conback 3: set black background
bonus points if we can ALSO set a rgb color.

Describe alternatives you've considered
alternatives are up to you.

Additional context
my eyes are getting old.

Impact on server or mods
nope

[Calinou]

I use cl_consoleType 2 in OpenArena which allows exactly this (setting a plain color of your choice), and I find the default Quake conback too noisy.