While it is true that flammable liquids produce black smoke, so does any petroleum-based product. The color of the initial flame and smoke might have been important in the 1940s and 1950s when our furniture was made of cotton and wood, but most furniture today is made of nylon, polyester, and polyurethane. Even wood fires, deprived of oxygen, will produce black smoke. Black smoke can also be produced by the burning of other materials including most plastics or ignitable liquids. Light smoke may indicate that there are no petroleum products burning.
Black smoke indicates nothing meaningful.
Distinct burn patterns . Distinct burn patterns may be produced on a tight surface by flammable liquids burning on that surface. However, the radiation from a burning fuel package can just as easily produce distinct burn patterns, even if flashover has not occurred. A major cause of distinct burn patterns is the protection provided by irregularly shaped objects, such as broken pieces of sheetrock wall or ceiling that fall on the floor during a fire. Clothing on the floor will also cause irregular burn patterns with sharp, continuous, irregular lines of demarcation between burned and unburned areas.