I mean, really, they're scales. What did you think was going to happen?
Their palettes don't match for one reason: So we can tell them apart. If not for trying to tell a story and clarity and yadda yadda yadda, I'd have made their palettes match through some manner of averaging out nonsense.
As for the resulting hair styles, it's not intentionally meant to look like old school Nanase hair. It's just what made sense to me as being as close to a middle ground between Sarah and Nanase's hair without looking like a complete mess.