As you can see, nothing new with the color scheme: the tabards will stay white with a black stripe in the middle when it is not hidden by the beard.
The only thing I've changed is the receipe for the grey beard:
- basecoat in GW Fortress Grey,
- shadows with a mix of Fortress Grey + GW Adeptus Battlegrey, then Adeptus Battlegrey + GW Graveyard Earth,
- highlights with Fortress Grey + Graveyard Earth, then Fortress Grey + Graveyard Earth + P3 Menoth White Highlight (a kind of ivory), then pure Menoth White Highlight,
- and finally, some washes of GW Devlan Mud to deepen the shadows.