(Photo: unknown)
The toothpaste brand Aquafresh is noted for its colorful presentation that comes out with every squirt. How does it work? To find out, freeze a tube, then cut it open. The colors run smoothly from one end to the other. So, to answer your question: magic.
-via Brian Ashcraft
Back in the sixties, I was an ever curious kid, and there was a brand of toothpaste called 'Signal', which had red stripes. I of course had to dismantle the tube to find out how it was done. There was a collar device in the tube nozzle that dispensed the red mouthwash sripes using laminar flow. However, the tube above is the result of a multi-nozzle shaped extrusion.