When the kit first came out the necelles had a yellow tinted bubble.  

i still have one of them.  Later on everything except the domes were white.  

For the episodfe "Doomsday Machine" they used the AMT kit for the Constellation.  You can see it if you watch the original series run before the upgrades were made to the episodes.

Oh very cool!!! 

I built two of those. Melted the second one trying to light it back before LEDs were readily available! 

That's a older issue of it. Has the larger deflector dish and smooth nacelles end caps.  Looking forward to it.