Each different aspect of Santa Muerte is depicted as a skeleton wearing a robe of her respective color. In the case of a seven-color statue, all seven colors are displayed; below these colors are listed in the order they appear from top to bottom on a typical seven-colored statue:
White: This color of Santa Muerte is used principally for purification and is called on at the inception of major projects, both mundane and magical. She is also used for certain types of healing.
Blue: This color of Santa Muerte is the patroness of the activities of daily living and the relationships on which our lives depend. This aspect increases social wisdom and increases patience. She is used to build long-term relationships and so is used to repair broken family ties, improve business partnerships, and gain new friends.
Green: This color of Santa Muerte is associated with justice, ethics, and law. She helps restore balance, imposes fairness, and can affect the judgement of both law courts and your peers. Because many people who pass through the criminal justice system are affected by addiction and mental illness, the green aspect of Santa Muerte is petitioned for issues resolving behavioral health issues.
Gold: Mining gold from deep within the ground is a dangerous occupation that can easily maim or kill; many gods of the underworld are associated with wealth and money for this reason, since mining was seen as taking gold from the pockets of the gods. As a goddess of the underworld, Santa Muerte has this relationship with money, and through it, vitality. The golden Santa Muerte is used to attract money and luck, create fortune in gambling and business, and heal where infusions of vitality are needed.
Red: The red aspect of Santa Muerte has a definite martial feel, governing issues regarding sex, lust, and passion as well as aggression and physical dominance. She also improves or impairs relationships, being commonly called on for this purpose.
Purple: The purple aspect of Santa Muerte is that of a goddess of both magic and initiation. She assists not only with spells but also with the direct understanding of magic. This Santa Muerte also acts as a gatekeeper between different ethereal and astral realms.
Black: This color of Santa Muerte is very Saturnian, overseeing all forms of cessation, negation, decay, dissolution, and denouement. The black Santa Muerte is used to negate bonds and barriers, as well as destroy or dissolve spells, curses, or hexes. She is also used for necromancy, such as speaking with the dead.
Source: Santa Muerte: The History, Rituals, and Magic of Our Lady of the Holy Death by Tracey Rollin.