The prospect of a redhead emoji was discussed at last week's Unicode Technical Committee meeting in Cupertino.
Option #1 appears to be the simplest method, which would involve the creation of a new, standalone "Person With Red Hair" emoji.
This would be able to support genders and skin tones.
Above: "Option 1" is one of the preferred redhead options from Unicode.
Option #4 involves the use of ZWJ Sequences, which could (theoretically) be extended to support additional hair colors.
A previous proposal to encode color swatches may be required if this approach is chosen by Unicode.
Above: Option #4 could permit additional hair colors.
A revised proposal focussing on these options has been requested for a future UTC meeting, and could be tabled for further discussion as soon as May 2017.