When...I don't recall seeing that.
Yeah... I went trawling through Trekcore to find a screengrab depicting that... but there wasn't one. I think I imagined it, sorry.
But I
have seen it - maybe in TMP?!
In any case, if the lighting scheme hasn't been revised (the deflector seems a lot brighter, but that could be more translucent paint in use there - great improvement!), then the impulse engine light is a warm white rice bulb, and the colour is inherited from the paint on the impulse manifolds.
It's a relatively small revision to re-colour them before release, and if it doesn't happen, I wouldn't be too upset.
Actually, let me use my umpteenth edit to look at the bigger picture on this one:
Yes, the saucer is still somewhat translucent to natural light, but the secondary hull and the impulse pod, that were practically transparent to internal light, have both been superbly and appropriately light-blocked, only allowing light through in the appropriate places, like the "impulse crystal" - which is outrageously fantastic...
Bravo, DST.