If there is a dynastic rule entitled “Color (or colour if you swing that way)”, add the following text to it:

If a Sheep is of Undetermined color, that Sheep may not acquire a Color of Black or White unless (i) that Sheep has, at some point prior to such acquisition of Color, had a Full state of Fleece, or (ii) the assignment of Color to that Sheep is effected by an Official who has the power to do so.

If there is a dynastic rule entitled “Fleeced”, add the following text to it.

Once 24 hours have elapsed since a Sheep of Undetermined color acquires a Full state of Fleece for the first time, that Sheep may elect to acquire either Black or White Color whereupon the Color of that Sheep becomes fixed and may not thereafter be changed.  If a particular Sheep is entitled to elect a Black or White Color by operation of the previous sentence but fails to do so within 48 hours of that particular Sheep having acquired a Full state of Fleece for the first time, any Sheep may assign a Black or White Color to the particular Sheep, whereupon once this has been done once, the Color of that particular Sheep becomes fixed and may not thereafter be changed.