First you have to print the koolaid picture (you dont need the whole picture, just the face)
then you need to get yourself some acetate, and put it over the face so you can cut it (make a stencil) and you will have something like this.
(mine is already painted because i took the picture while making the shirt)
you paste in on the shirt with masking tape (dont forget to put some cardboard under the fabric so the paint wont trespass)
repeat the same process for al the faces, doing 4 faces of each color of the rainbow (red, orange, yellow,green,blue,purple)