Hexproof from [quality] is a protective keyword. A creature with hexproof from black can't be the target of black spells or abilities your opponents control; hexproof from white works the same way against white spells and abilities. Hexproof from monocolored stops opponents' spells or abilities that are exactly one color. It only blocks targeting—opponents can still affect that creature with spells or abilities that don't target it, such as board wipes, or with effects you control.
In play, this ability makes a creature a reliable threat against certain decks. A knight with hexproof from black dodges black removal, while hexproof from monocolored can blank a wide range of single-color answers. Because the protection is narrow, it rewards knowing what your opponent is playing—and it forces them to find answers outside that color or quality.
