Blot the Kool-Aid stain with an old towel or rag as soon as it happens to try to get as much of the stain up as possible.
Make a mixture of ½ cup distilled white vinegar and ½ cup water and blot the mixture on to the Kool-Aid stain. Put another towel under the fabric or inside the fabric to help keep the Kool-Aid stain from spreading further in the fabric.
Leave the vinegar and water mixture on the fabric for 10 minutes.
Pour a little hydrogen peroxide at a 3 percent solution onto a new clean cloth and dab at the stain. Let it get wet but don't go nuts -- it doesn't need to be soaked.
Use your vinegar solution to gently rub at the stain after the hydrogen peroxide has been applied.
Get another cloth and dampen it with cold water. Gently scrub at the stain and the Kool-Aid should be gone.
Pre-treat the clothes with some stain removal treatment and let it sit for awhile. Then wash it in the washing machine with regular laundry detergent and check for any evidence of the stain before drying it. If you see any traces of the Kool-Aid, repeat the stain removal product and washing procedure until your clothes are nice and clean again.