Humbrol AV0003 V0003 Weathering Powder Sand

Pigments are used to add realistic effects, the effects of weathering, aging, vehicle finishes, fortifications and structures in modeling.
They are perfect for creating the effects of accumulated fresh or dried dust and mud, dirt, corrosion, ash, water stains, sooting, produced by time and natural erosion.

A pigment is simply a dust, a powder obtained from various metals (e.g. magnesium, zinc, titanium) and minerals, used to produce all colors.
The difference between a pigment and a paint is explained by a simple explanation, a paint is a pigment combined with a substance that "clumps" its particles and allows it to adhere to painted surfaces.