Well that's too bad that things in their archives have an "expiration date". PBS has a history of fantastic stuff that it would be nice to still have. Instead it sounds like it just gets thrown away after a while. Pretty sad.
More likely returned to their creators, judging by how many old shows have home video releases and/or reruns (including Reading Rainbow).
I emailed Steve Horelick through his website, and Dennis Neil Kleinman through his YouTube channel. Kleinman responded first, and unfortunately admitted that he only knows of PBS showing two versions. However, I didn't show either of them this thread.
I think the second intro would have aired during some time between 1999 and early 2001. The only differences I remember include: * The beginning showed the dragon and the butterfly flying, instead of LeVar reading a book. * The butterfly's trail created the rainbows, instead of them appearing to come out of nowhere. * The boy looking through the telescope saw the dragon winking, instead of LeVar. * The shot of all the kids reading together had the dragon in the upper-left corner, instead of LeVar.
Regarding the theme song: * More guitar twanging throughout * "Friends to know/And ways to grow" sung without a pause * The last instance of "Take a look/It's in a book/A reading rainbow" sung with longer pauses in between each line. * The end had an updated version of the first theme song's synth intro and ending.
LeVar still hasn't responded to my Tweet, and a post I left on the Reading Rainbow Facebook page also has no replies.
I have one piece of lost media I've considered writing about, but I don't have much proof that it existed. I seem to recall that one season before Reading Rainbow changed their intro to this:
PBS aired a version with some differences. It used a new cover of the theme song, and had some appearances by a CGI butterfly and dragon (the latter of whom wore glasses). A new instrumental of the theme also accompanied the end credits. The next season, the singer and instrumentation changed again, and the CGI creatures disappeared, to essentially give more screentime to LeVar Burton, and the eponymous rainbow. Right now, the only evidence I found of other people remembering the second intro came from comments posted at the aforementioned YouTube link. I tried asking LeVar on Twitter if Reading Rainbow used three intros, or only two, but he has yet to answer. Can I write an article about this, or would I need more proof of its existence? Not even Wikipedia or TV Tropes mention it.