Well afaik 'chroma' is limited to visuals, so 'monochromatic games' should be specific enough, but then you never know what tutors will pick up on.
thanks for pointing it out! so I should call it "... games with monochromatic visuals..." ? to generalize it as much as possible?
If this is a formal paper, it may be worth differentiating between black & white (two colour) and monochrome (black, white and grey), as in the field of computer graphics at least they're different things. Black and white movies are monochrome not black and white to a scientist. You could just replace b+w with monochrome in your text though, as b+w is a subset of monochrome.
Does make it a bit more complicated for games like Vorpal though, which seems to be black & white + various shades of red.
I don't have any games to add to your list though, sorry.
I've not seen Madworld in action, but yes in the video of Vorpal I spotted of light shades of red (red->pink) and dark shades (red->maroon), so I'd say black, white and shades of red would cover it. In videos on Unfinished Swan though, I've seen black, white and plain yellow, though I've not seen later levels (no spoilers please so perhaps it's more than those three colours (and perhaps there are shades of yellow - I may be misremembering).
and...for "Vorpal" and games with some additional color it might be... "B+W and shades of XXX color"? (Madworld then is this one too)