To study the colors of a soap bubble it is great to have a light table (See a light table in action here), and it is easy to make it.
You will need:
Make sure to check how hot the light bulb gets when you do the experiment, so that the plastic box is not melting.
IMPORTANT: Make sure that the electrical parts (wire, mounting and bulb) does not get in contact with the soap bubble juice
Put the bulb in the box and lead the wire out (if possible through the a hole in the box, see the photo below)
Place the plastic bag on the top of the box and led the rubber band hold it. Stretch the plastic bag to make a smooth surface.
Turn on the light and make the top surface of the plastic bag wet. Now you are ready to make beautiful soap bubbles on our light table.
Any use of this description on your own responsibility.