The 11 Year Soap Bubble

-Overdrive- writes "Popular Science has an interesting article about an inventor and his 11 year quest for Colored Bubbles" From the article: " It turns out that coloring a bubble is an exceptionally difficult bit of chemistry. A bubble wall is mostly water held in place by two layers of surfactant molecules, spaced just millionths of an inch apart. If you add, say, food coloring to the bubble solution, the heavy dye molecules float freely in the water, bonding to neither the water nor the surfactants, and cascade almost immediately down the sides. You'll have a clear bubble with a dot of color at the bottom. What you need is a dye that attaches to the surfactant molecules and disperses evenly in that water layer. Pack in more dye molecules, get a deeper, richer hue. Simple. Well, on paper anyway."

That is only half of the problem

[nietsch]

And the inventor solved that early on. Indeed the dye has to be attached to the soap or else the relatively heavy dye will sink to the bottom of the bubble to form a dark spot in a clear bubble.
The other problem (if you'd read TFA you'd have known) is that parents do not like it much if their kid comes home when it is splattered with your dye, no matter if it washes of easily. He solved that problem with a dye that can switch between colored and uncolored.