Since we started candy experiments, my daughter is now in the habit of reading ingredient labels. Last night she read the label on the egg dye kit. "Mom," she said, "they only have dyes in red, yellow, and blue. So the orange, green, and purple must be mixed colors. Let's do chromatography on them!"
So, last night while I was cleaning up the mess, I got out my coffee filter paper and tried it. Indeed, I can see a faint but clear separation for purple, and maybe for green as well. Orange isn't so obvious, and it might be that one of the yellow dyes in the ingredient list is really orange (we certainly see orange after we separate M&M brown, even though no "orange" dye is listed.)
If anybody wants to try this, I would recommend wetting your dye tablet and dabbing it on the paper BEFORE you dissolve it in vinegar. You should get more intense color than I got using the dissolved dye, and the color separation might be easier to see.