It's as if you got flour blown in your face. Lighter or darker, smoke creates a softly blended marking on all limbs, with the minimum being two.
Specifications and Rules
The minimum of two points can appear on any limb, so combinations of, for example Face + Tail, or Tail + Legs are all acceptable. But when including legs in the combo, don't forget that the symmetry rule calls for at least two legs to be affected. Color may not change from limb-to-limb.