Well the Excelsior's nacelles were glowing in Farpoint and Flashback, so maybe I'm remembering other eps where they were glowing.
The Excelsior nacelles didn't glow in Farpoint. They only glowed in Flashback (using a different model), and going forward in DS9 (CGI).
Here they are glowing in FLASHBACK
an error in many ways, not the least of which being that the Excelsior's nacelles didn't glow in TUC, during which the past segments of "Flashback" take place.
we see the nacelles glowing in DS9's "Paradise Lost."
Again a feature of them switching to CGI and not staying "true" to what was previously established.