if more than one bit of color was allowed you could make different levels of grey/opacity hint at where the opening in the symbol should be. just as learnable

if more than one bit of color was allowed you could make different levels of grey/opacity hint at where the opening in the symbol should be. just as learnable and now it's unique. taken to a silly extreme, you could compress 26 letters into 2 pixels, 3 colors, and 3 levels of opacity. before even considering a time-dimension. a mantis shrimp just needs one pixel with color.