What You Did
You looked at a candle flame through the tiny space between two pencils.
When you looked at the flame through the pencils, you saw a tiny rainbow. When you pinched the pencils closer together, you saw black blobs form between the colors. You saw the different wavelengths of light as separate bands instead of the usual stream of white light.
If you didn't focus right or if your pencils weren't close enough together, you may not have seen the blobs.If you used a light source other than a candle flame, you may not have seen them either.
See if there is a difference between a natural-color hair and an artificially-dyed one.