Interesting idea. I don't know if it's really worth doing, but it might be. I was just now thinking about how it could be done. Unlike a tube of paste, shaving gel is a liquid in the can. It may be thick, but it will still mix up if you shake it. This would make it hard to keep the different colored gel from mixing in with the rest. It might be possible to make the different colored gel lower density than the rest, so that it will always tend to float to the top. Then it won't come out until the end (I assume that the cans have a tube that draws the gel from the bottom of the can like most aerosol cans). However, the gel might be too thick to let the lighter material float up through it. Maybe they could put the gel in a transparent or translucent plastic bottle. Then it would be obvious how much is in it.

Modern shave gel cans actually do not have a tube that draws from the bottom of the can. If you turn the can over and look at the bottom you will notice a rubber nib in the center of the can. This nib actually holds in the pressurized gas that is behind a plastic plunger. When the product us used a valve is opened at the top, creating a lower pressure atmosphere to the outside of the can and the product comes out as the gas behind the plunger presses the plastic diaphragm up.

In terms of multi-colored/muti-density foams you have to think about the manufacturing process. These cans are filled at speeds of up to 60-100 cans per minute. Even if two separate nozzles were used to dispense the two different color gels into the can, the high-speed filling rate would mix the colors instantly.

I recommend buying two cans at a time and keeping a spare under the sink in case you run out.RussPackaging Engineer