So I'll do 5D then. In fact, I'll do n-D. It's all the same maths, really. And visually you can represent 6 dimensions on-screen without any loss. 3D using magic-eye, and then 1 more D for each of R, G and B. It's too confusing to be of any use, but for 4D (3D and greyscale) it works. Oh, and a 5D cube can be found