I don't care about hair color at all. Age is variable, since an older Lois can have just as much of a fun dynamic with Clark as one his age. Race can also be variable.
About my only thing is I’d want certified for the character is a sassy, sarcastic, very sharp Lois who’s “hungry” as a reporter, and who might express a healthy appreciation for Superman as a sex symbol (perhaps contrasted with Cat Grant’s more overt “thirst,” and thus coming off as a still-professional in comparison) while having a clearly more sitcom-like, sometimes belligerent unresolved sexual tension with her close and mildly vitriolic friend Clark.
When it comes to her actual relationship with Clark and Superman in detail… we’re not doing any stupid Silver Age bullshit, and instead going hard after the Golden Age, Bronze Age, and Post-Crisis type of relationship:
-First, I’d make the visual differences between Clark and Superman distinct enough that it makes sense she wouldn’t suspect him when no one thinks he has a secret ID (contact lenses, a tan, filming the scenes at different times around the actor getting jacked for the role, background basic white guyswith glasses, maybe even lookalikes or stuntmen). Here, she has a very controlled and distant church of Superman, and starts getting close to Clark.
-Second, when there is proof that Superman has a secret ID, it’s right when she and Clark are getting closer, and when she suspects it, she pretty much immediately knows for sure but can’t prove it, with that creating further belligerent tension with Clark. I’d even have the irony be that Clark was about to tell her, but because she beat him to the punch and now feels insulted and deceived, it sort of causes a mild break-up and cat-and mouse game… but played with in that Lois isn’t selfish enough to let her tricks inconvenience him saving the day, showing a soft spot she still has for him. She may even start to traction out of hating him by helping to cover for him against Luthor.
-Thirdly, eventually they both hit a point where they regret fighting over it, and we get a hilarious transition between their fighting and cat-and-mouse game and just giving into their attraction to each other and desire to trust each other again, and she becomes his confidant again.
And for actresses I’d consider…
Aubrey Plaza