Neat idea, but I think the execution could use a bit more work. Mostly it generating impossible levels. Maybe also having the levels generate themselves once and not having the player stop the generation on a level would help, but that would be something to experiment with.
Also I think it would've been better to use primary colors (Red/Blue/Yellow) as bases instead of computer colors (Red/Green/Blue). I always think of color mixing in primary colors, and had to always remember that, for computers, yellow is a mix of red and green, instead of mixing red and yellow to get orange, and blue and yellow to get green.
Also, not too sure how well this relates to the theme of the jam. The title is "Only Red Causes Death", but you immediately subtitle that with "Only (that which contains) Red Causes Death", which means that not only red causes death. There are then 4 colors to avoid in the game, which is not 'just one', as the jam theme indicated.
I do think this could be a neat little game if it was fleshed out a little more, however.