Rockler Woodworking store. Or Rodda paint, Sherwin Williams, Dutch Boy, Miller, how many ways can you say paint store.
White: Whiting
Light grey: Pumice stone
Darker grey: Rottenstone (grey)
Red or Ruder: Rottenstone unbleached
Also good is pastel chalks applied with paint brush and scrubbed in. Light overcoat with flat fixative.