blacken

(verb) make or become black. Synonyms: melanize, melanise, nigrify, black. Examples: "The smoke blackened the ceiling." "The ceiling blackened."

(verb) burn slightly and superficially so as to affect color. Synonyms: char, sear, scorch. Examples: "The cook blackened the chicken breast." "The fire charred the ceiling above the mantelpiece." "The flames scorched the ceiling."