Discoloration encompasses all types of surface related effects that lead to unexpected color changes. These include a darkening or gray color from surfactant leaching, white efflorescence on masonry, white or black color over caulk, black color over masonry patches and drywall joint compounds, red color (tannin bleed) over cedar and redwood, brown or black color (wax bleed) over hard board, yellowing of white paints, a wide range of color change when non-durable organic pigments are used as tinting colorants, and a premature loss of color when paints are applied over heavy chalk residue.
 

Color changes are used as indicators for determining the cause of the problem. Some can be paint related, while others are substrate (or surface) related. Color change does not mean that the protective quality of the paint film has been altered.