A hele-shaw etalon lens created by Timm Vanderelli was suspended on glass. The lens sandwiches a layer of nano-sized magnetite particles.
Neo on lens using just 5 LEDs of different colors.
I set 80 lensed white LEDs into a plastic colander to provide multiple points of light. Every 5th position also had a colored (red, yellow, etc.) light for calibration. Polished tubes directed the light more accurately.