Your question is a good one, and I'm probably not going to help much, but here's my thinking on the "original" light. There are probably a few different concepts involved here, so I'm pinging those who know this far better than I do. The well-known background radiation is as original as it gets, and although it isn't in the visible range of the spectrum we can detect it. Why hasn't "left us behind"? Why is it just now getting to us? If it were invisible, that would mean that it is so far away that it hasn't yet had time to get here, which would imply that the universe expanded faster than light. But by the time the first light was created, the presumed inflationary FTL expansion had ended. So it's within range, thus visible. Does that help? I didn't think so. Someone will pop up and explain it to us both.
Thanks. We do have some brilliant people here. Perhaps we have our own version of Isaac Asimov.
(As a youth I really enjoyed reading Asimov's "science fact" essays, because he was so good at explaining the difficult scientific principles of our day).