Here’s the early Vulcan orange-sky design - still with at least one giant moon:
Kind of the reverse of what happened on Forbidden Planet. I recall a Cinefantastique article saying the FP script called for a chartreuse sky, which was faithfully depicted in the cyclorama on set. But there were also B&W storyboards of the surface of Altair IV, which called for a “blue-black sky” with “large planets” against a starry backdrop.