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.
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.