Kool-Aid.
I had a leftover big and boring skein of natural color wool and, as I was contemplating how to mutilate it in the most entertaining way, memories of chameleon hair came to me. So I surfed on over to Google and typed in "Kool-Aid dye yarn" - which came up with a mere 24,000 results. After reading a few of the more promising looking entries, I devised my color scheme. Next grocery store run, I stocked up on assorted flavors and colors of unsweetened Kool-Aid and got a box of gel food coloring for backup. Then I bided my time...The problem, you see, in any colorful endeavor is the Engineer. He's just a wee bit anal retentive when it comes to project cleanliness. Whenever he's working on something in the house, the vacuum cleaner is sitting right next to him and he uses it constantly. Neither crumb nor grain of detritus escapes his radar sight. Every night after I cook dinner, he looks at the kitchen and announces that my middle name is "Mess." Imagine the high hysteria should he realize I was planning to dye something.
When The Engineer was out of town for several days, I used my yarn twaddler (alias: swift) to take the sacrificial yarn from its skein and turn it into a long hank. Using the two ends, I tied the yarn securely into a big loop.
Now, I've got to admit that the Engineer does have some basis for saying my middle name is mess, so I decided to do the potentially dirty deed outside on the picnic table instead of in the kitchen. If worse came to worse, the sun should eventually bleach any sins from the wood.
Following what I had garnered from the web, I soaked my yarn overnight in warm water with a bit of dish soap and rinsed it the following morning, being careful not to rub or squeeze it since it was not superwash. I boiled water in my big stainless steel pan and added a packet of yellow Kool-Aid and mixed up food coloring in a couple of tablespoons of white vinegar to make a brown color. I thought I would have more control mixing small drops of food coloring than I would with packets of Kool-Aid.
I placed my biggest Pyrex pan on the newspaper and garbage bag covered picnic table and arranged about half of the wet yarn in it, then I poured the food coloring in a long "S" shape over it. A couple packs each of blue and green Kool-Aid were sprinkled around the brown and some orange went right over the brown food coloring to brighten the color. I flopped the rest of the yarn into the pan, sprinkled it with my last few packets of blue and green Kool-Aid, then poured the hot water (with yellow Kool-Aid) over it. After stretching plastic wrap over the pan, I placed it on the cement in full sun to cook all day.
By the end of the day, the dye water was clear and the Pyrex pan was so hot I had to use pot holders to move it into the kitchen. 
Once it was cool enough to handle, I drained it, rinsed it, and squished the water out using an old towel. The wool was then draped over a wooden drying rack until thoroughly dry. I put it back over the yarn twaddler and made an oversized muffin out of it.
Final analysis: No mess was made, not even any stains on the towel - yay! hurray! Overall, the wool came out much lighter than I had expected. Very little of the blue Kool-Aid stayed in the wool, though the green, orange and brown did well. The colors were less neon than many web sites had warned to expect, more pastel.
I think it looks pretty darn good.
