Easter egg dyes can be fun to use for accidental or purposeful dyeing. The headband shown here was spun up from bits of wool stuffed into the remains of the easter egg dye pots one year. I simply added an extra glug of vinegar to each of the little plastic cups, stuffed a bit of wool in, microwaved them for 4 minutes (2 on, 2 rest, then 2 more on), then rinsed the wool out and laid it out to dry.
Check the ingredients in the dye, they are usually in very small print on the box somewhere. If it has citric acid, then you won't need to add as much vinegar or citric acid to the dye. I'd recommend still adding some, just to be safe. You can add either one if you want to make sure there's enough acid for the dye to strike, or pre-soak your wool in a sink full of water to which several healthy glugs of vinegar have been added.
Easter egg dyes are acid dyes, so they work much like kool-aid dyes or commercial acid dyes. I'd recommend pre-dissolving the dye pellets in warm water before mixing them into your dye bath or painting onto the wool.
Or, for a very striking result, you might try this:
Presoak your wool in a warm water/vinegar solution, ensuring it is completely wet. Crumble easter egg dye pellets onto the wool, and pour on more warm water/vinegar to ensure it is soaked but not sloshy in wool. Wrap it all up in plastic wrap, and in a non-food microwave, on high power, run it 2 minutes on, rest 2 minutes, then 2 more minutes on. Let the microwaved wet wool cool in the sink without any water, then unwrap it and rinse it in lukewarm water until the water runs clear.
If you prefer not to microwave, place the crumbled-upon skeins into a non-food steamer and steam them for 30 minutes to an hour, then cool them and rinse them as described above.
This technique of crumbling the pellets onto the wool will lead to quite rich, but incomplete, coverage.
Also, I've noticed easter egg dyes do split, where the mix of colors in a dye pellet separate and are taken up by the wool separately, so instead of a purple, for example, you'll get a red and blue streaked fiber. You could recard it into a purple, or enjoy the variegation.
For a solid-color dye, I'd dissolve the pellet(s) in warm water, then add more water and vinegar, bring the dyebath up to steaming (sub-boil), add the wetted wool, and let it steam (not boil!) until the dye bath is clear -- yes, the water does clear, as the wool takes up all the dye! How cool is that. I'd expect easter egg dye pellets have filler in them, so it would be hard to say how much wool they would dye a medium shade; if you don't use enough, you will get pastel hues, and if you use too much, the dye bath won't become clear. So if it isn't clear after about 45 minutes, you've used too much. If your wool is too pale, you can add more dissolved pellets and let the wool take up more dye. Now, if the dye in the pellets split, your "solid color" wool may end up odd colors.
There are some great solar dye experiments done by Rita, you could try that method with easter egg dyes.
Since easter egg dyes are acid dyes, you can also use them to dye silk, nylon, and other animal fibers. If you use them to dye a wool/tencel or a wool/cotton blend, the tencel won't take up the dye, so you will get a tweedy effect. That's cool, too!
(expansion of a recent post by me on dyehappy)