More specifically, it seems to be affected by the in-game sun lighting effect (just tested this on Esamir): Smoke particles seen with the sun in front of you, are almost completely black. Inversely, smoke particles seen with the sun behind you, are almost completely white. To observe this effect: Have particle quality at Ultra. Spawn a vehicle. Drive around with the camera facing the same direction of the sun, and then drive around with the camera facing the opposite direction of the sun. Notice how the smoke colour shifts between white and black.
