heres the actual CGA spec
wiki link
There are a number of different modes depending on the resolution used, even a 16 color mode.
so... It would probably be a good thing for you to look at the spec and decide resolutions that should be used?
For this jam and as appear in rules you can use any resoluction and only choose between 2 color palettes.
To be clear, this means 16-colour mode is not allowed.
16color mode is not allowed, only 4 colors in screen to choose between two palettes ;)
