The Kool-Aid mustache is a manifestation of artificial coloring (and sweeteners) on the upper lip of the patient. The most common color is red, but purple, blue, and green have also been known to make an appearance. A yellow mustache is non-existent, since it almost impossible to stain.

Cause

The mustache is caused by putting too much of one's face into the cup of Kool-Aid. The drinker needs to only tip their cup far enough so that they are able to easily sip their refreshing drink. Tipping it too much will cause the artificial coloring to make prolonged contact with the upper lip causing the mustache. A stop-gap measure would be to use a straw.

Many a small child spends most of their younger years with a semi-permanent reoccurring Kool-Aid mustache on their upper lip. It is similar to the milk mustache, but has never been used by Kraft Foods to push their product (not unlike the National Dairy Council).

Treatment

A small amount of toothpaste rubbed on a wet washcloth will get out the mustache every time. Guaranteed to get out most any stain, even ones Jim Jones can conjure up.

References

http://www.geocities.com/donovn1/koolafaq.html - The Kool-Aid FAQ