Prepare each layer of jello according to the package directions. They directions should be similar to: empty one jello packet in a bowl, heat water to boiling, measure out 1 cup of boiling water and add it to the jello powder. Stir until the powder is dissolved. Add in 1 cup of cold water, and stir again.
Pour the jello into a 9×13 inch pan. Be sure that each jello layer sets before adding the next. Add the layers in this color order: purple, blue, green, yellow, orange, red.
Once all of the jello is set, slice it into squares and serve.
Notes
NOTE: DEPENDING ON HOW THICK YOU WANT EACH LAYER, YOU MAY HAVE LEFT OVER JELLO. I DID NOT USE ALL OF THE JELLO FOR EACH LAYER, I JUST TRIED TO MAKE THE LAYERS EVEN.