I'm not sure in which SE site put this question.
Imagine a typical child toy, where a bunch of spheres move by gravity through a labyrinth.
Now imagine a sealed small labyrinth with two fluids. I'd like to reproduce the concept of one fluid moving through another forming small bubbles, but I don't know which common fluids might be useful. Theose two fluids should not mix, the viscosity must be low (so the bubbles can move easily), both fluids must have different colors, they must have different density, the bubbles should not stick to the plastic of the labyrith, it should work at room temperature, and -if possible- I'd like to see many small bubbles instead of a single big bubble.
Which two common fluids might be useful? I tried air inside water (few bubbles and movement too fast), I also tested water inside kitchen oil, but it moves too slow and the colors aren't quite different.

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    $\begingroup$ If kitchen oil is too viscous, try kerosene, paint thinner, and so on. Don't bother about color. After all, any liquid can be colored anything. $\endgroup$ – Ivan Neretin May 30 at 19:27
  • $\begingroup$ You can also increase the viscosity of the water by addition of sugars $\endgroup$ – Andrew May 31 at 10:54
  • $\begingroup$ You can at least colour one phase after you identify a suitable couple. $\endgroup$ – Alchimista May 31 at 11:50