I don't think Nanette is trying to create any highlights, rather modulate the colour of the existing hair node specularity - much like the method of using a noise node  in the root/tip.

I've done a similar trick here for a different effect, to give the hair a mix of grey hairs. You can plug all kinds of procedural or image map nodes into the hair node to vary colour, create streaks etc.

There were some good threads a year or so ago detailing some of these variations.

 

PoserPro2014(Sr4), Win7 x64, display units set to inches.

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