Light reflected from both faces of a soap film — a few hundred nanometres of water held in a wire loop. No colour here is chosen: each pixel integrates Airy reflectance over eighty wavelengths, the film is carried by an incompressible flow, and gravity drains it, top first, toward Newton black.
This piece is computed live on the GPU and needs WebGL2 with floating-point render targets. A current desktop Chrome, Firefox, Edge or Safari will let it breathe.