Sounds like a director/cinematographer's choice more than yours. The screenwriter's role is to build the story, right? So unless that sky has an absolutely irreplaceable effect on the scene (unlikely) or it has strong thematic resonance that truly elevates the work (unlikely) you're getting too focused on details.
Even a third-person novelist, who has license to describe anything anywhere, still has to have a reason for describing. In Old Man And The Sea, Hemingway spends a lot of time describing the ocean, the sky, ocean birds, but the descriptions function as more than just that. They communicate the passage of time, and accent the almost insane solitude the protagonist endures on his adventure of absurd persistence. In any other book those descriptions would probably hurt, not add.
If you have an amazing, just brilliant vision of the scene and how the light makes it unique, then suggest with a minimum of description. Be prepared for it to be ignored. No reader or agent gives a s*** as I understand it. They are bloodhounds for story structure alone, and the script will be re-written by someone somewhere.