@MJTiny this is a regular request here so hopefully it's being noted. We sometimes talk about the colour sliders that can be used to change make up and skintones and how great it would be if we could use those on hair in particular, but I think they could be used for eyes too.
I say it a lot but I miss the way we did it in Sims 3 CAS. I loved being able to create highlights and lowlights myself when adding hairstyles to my Sims.
I like to set different styles for each outfit category and the current hairstyles with added highlights, brighter shades or ombre styles can tie you to just one style because it changes colour in another so it would be great if we could just alter the colour ourselves.
I believe we'll see it in Sims 5.