You could click through the different platforms bubble bobble was released for on mobygames to see which one looks familiar. The DOS version seems to have had a

You could click through the different platforms bubble bobble was released for on mobygames to see which one looks familiar. The DOS version seems to have had a CGA 4-color mode but it wasn't cyan/magenta. Amstrad CPC looks like a candidate: https://www.mobygames.com/game/cpc/bubble-bobble/screenshots https://www.mobygames.com/game/cpc/bubble-bobble/screenshots