The image is a four dimensional torus, projected onto two dimensions.
The colors emphasize the cusps and caustics associated with the projection.
This image is taken from Eric J Heller's website which is filled with lovely images, inspired by familiar topics like the one above, but also other current research, such as quantum chaos.
Eric Heller is on the Physics faculty at Harvard. Much of the website is geared
towards making the casual found objects of physicists (and mathematicians) into beautiful images.