With the exception for audio and questions about similar things with vibration and such, I think there's a better way to rule it that allows all this. The main limitation I feel you are going for in the jam is "One bit of output", and the rules about how to display the screen are just to enforce that. I think it would be reasonable to have as many different outputs as you like as long as these outputs perfectly match which colour is on screen. In fact I don't even think having a screen at all should be mandatory. As long as there is only 1 bit of output since that's what the jam is really about, "the minimum (non-zero) feedback that a game could possibly have."
Some examples of 1-bit output that I feel should be allowed (as long as they all match if you use more than 1):
- Visual: switch between 2 colours
- Audio: on/off or two sounds
- Vibration: on/off or two intensities.
- CD drive: in/out (the time it takes to move would make this awkward though. If you rapidly switch you could make it stay at certain lengths; although this is still 1-bit, the drive itself converts the 1-bit into different info.)
- Fullscreen: on/off (this is getting silly but you get the point)