It is a universal past time for children all over the world (and sometimes even adults; especially those associated with kids) to make soap bubbles and play to their heart's content. Colored bubbles would naturally be an added attraction for them. Normally it is not possible for them to have this add on value for their bubbles, as producing colored bubbles require the use of some chemicals. In addition such chemicals need to be handled safely and carefully. The making of colored soap bubbles should be done only under the supervision of knowledgeable adults such as a parent or teacher.
Food coloring has generally been tried by many enterprising kids as well as people in order to have some colored bubbles. But this does not usually deliver the desired results. Also bubbles produced using food colors cause stains on the ground landing, on clothes etc.
There is, however, a simple way to produce colored bubbles using some chemicals. After landing, the coloring agent will disappear due to reaction with the atmosphere and no stains will be left behind.
The following items are needed to make colored soap bubbles.
Any common liquid dishwashing detergent, water and/or any commonly available commercial bubble solution
As per normal practice for soap bubbles, the first step is to mix the soap powder (detergent) with water. The second step is the addition of an alkaline chemical. To your bubble solution, made already with detergent and water, add sodium hydroxide and indicator.
You should have sufficient quantities of indicator so that the end product bubbles will come out with a good intensity of coloring.
For about four cups of the bubble solution, we need to add about 1-1/2 to 2 teaspoons of phenolphthalein (for red colored bubbles) or thymolphthalein (for blue color bubbles).
Continue to add on the sodium hydroxide until the indicator changes from colorless to colored (about half a teaspoon should be enough to accomplish this).A small additional quantity of sodium hydroxide will help to produce a soap bubble which retains the colors for a longer time. If you add too much, the color of the bubble won't disappear when exposed to air or when you try to rub it off from clothes/ground etc.
Sometimes it may be necessary to dissolve the indicator in a small quantity of alcohol before mixing it with the bubble solution. We can also use pre-made indicator solution, adding the sodium hydroxide to the indicator rather than diluting with water.