Try to get hold of some Vellejo Pale Flesh from their Game Colour range then wash with
GW Seraphim Sepia.
Use Bleached Bone to highlight the scars then use
GW Red Glaze to carefully go over the scar using a damp brush to thin out the edges to get this sort of blending (wrong colours I know but the principle's the same):
BTW Pale Flesh looks like this: