This shows two effects. The first is the effect of increased velocity from the same position in front of the square lattice. Note how the square lattice approaches a spherical shape near the speed of light. The prediction as one gets vanishingly near the speed of light is that the entire universe collapses into a singularity in front of you...so it's not surprising that it gets round first. The second effect of increased velocity from the same position in front of the lattice is that of light frequency doppler shifting based on the fact that parts of the lattice are further away. This accounts for the color changes. There is a final snapshot in this animation of a view much closer to the lattice.