When you add the hair model onto the Scout in the SFM,right click it's animations set,choose 'Add Override Material'.Then,right click on it again,and click on 'Show in Element Viewer<Model'.Once you reach there,click the plus by 'materials' (at the bottom of the list),then click on the plus by 'scout_pilgrim_hair'.Finally,there should be a '$colortint_base',mess around with that for your desired color.

Thanks!