Honestly, I just want them to implement non-natural hair colors for Child and Toddler sims first. Then, yes, I'd like to see a broader spectrum of colors added--a pale pink and a magenta, a mint green and a forest, a deep purple and a medium violet, and a navy blue...all to give us some more shades to work with in the unnatural colors.
With all of the official hair styles that have been released, it'll take some time. But...well, all that they'll really need to do to recolor all of these styles will be taking the texture files into Photoshop and adjusting the colors using Hue and Saturation with the Colorize option checked. Hours of hard work to get the colors to match up right, yeah, but it shouldn't take more than a year to get the unnatural colors ready for the Children and Toddlers. Then, maybe another 24-36 months to get new colors ready to roll out for all hair styles for all ages...and that's an estimate based on if they only put, like, one person on the assignment. (And, yes, I know what I'm talking about here, because I'll soon be graduating with a degree in Graphic Design, so I know how long a simple color correction/matching job in Photoshop tends to take.)