Is it considered witchcraft if a wife washes her husband's white clothes with her colored underwear, and there is a strange blackish-green substance and a strong incense smell in her room, and her husband's behavior towards her has changed?

Doubt that a brother's wife has bewitched her husband does not constitute a ruling. If certainty is reached with conclusive evidence, the ruling on this is mentioned in Fatwa no. 42899, and the legitimate incantations (ruqyah) in Fatwa no. 32690. However, if it is mere doubt, then extreme caution must be exercised against causing discord between the spouses, as separating them is one of the major sins, as Ibn Taymiyyah warned. Caution must also be exercised against slandering the woman unless her matter is certain, for "Every Muslim's blood, wealth, and honor are sacred to another Muslim," and "Beware of suspicion, for suspicion is the falsest of speech."