Pretty picture: Euphorbia pulcherrima 'Picasso'

I've probably done this variety, and similar varieties, of poinsettia an unkindness in the past by assuming it was one of those spray-painted ones. Spray-painting poinsettias is wrong. It's doublesuperwrong if it's spray paint of a color that poinsettias don't normally come in, and triplesuperplusnastywrong if there's glitter involved. I have no logical basis for saying this: it's just self-evidently bad.

But this, in fact, is just how this particular variety is. I've been looking for information on this type of variegation (what genes, if any, are involved? How does the plant decide which cells to pigment and which ones not to?), and all kinds of other variegation types, for some time now, but I haven't come up with much. It's possible that periclinal chimeras are the only ones I'm ever going to understand.

Still working on it, though. And there's always Barbara McClintock, if I get really desperate to explain some plant colors, though I'll have to understand it myself before I can even attempt to explain it to anybody else, and that may take a while.