Another way is to realize waves of different frequency are literally orthogonal vectors. Also, RGB colors form a literal color space. So at the cost of sacrific

Another way is to realize waves of different frequency are literally orthogonal vectors. Also, RGB colors form a literal color space. So at the cost of sacrificing normally colored objects, you can have rainbow banding in the 4th direction. Imagine along the 4th dimension there's a hallway with evenly spaced lightbulbs tinted in RGB such that looking down the hallway you see rainbows. If you are moving in the direction of the 4th dimension, these rainbows will appear to be moving like waves rushing towards you from the vanishing point. If you are moving perpendicular to it, the bands of rainbow colors will remain constant relative to your motion. In general, the apparent speed of the background color banding patterns will be proportional to the component of your motion in the direction of the 4th d. The rings of rainbows are easily spaced, so looking at the scene you can tell how far along the W axis it is by seeing how tightly the rings are bunched (must be approaching vanishing point if they seem close) and also by just eyeballing how often the rainbow has repeated between your position and the object, judging distance as if you were counting floor tiles.