Flora dresses in red, and appears to be the leader of the group. She seems to deal heavily with flowers and nature, based on dialogue, and her favorite color is pink. Fauna dresses in green. She appears to be 2nd-in-command to Flora and quieter than the others, and often functions as a peacemaker between Flora and Merryweather. Merryweather dresses in blue, her favorite color. She is feisty and pessimisstic, and is often seen arguing with Flora.
As a group, they all have powerful magical abilities, channeled by their wands. They can do many things, such as shrinking, bringing inanimate objects to life, and putting people to sleep. Their wings, naturally, allow them to fly. Flora and Fauna stated that they could only do good things with their magic, which seems to be contradicted by Merryweather turning Diablo into stone. However, as Diablo was evil and worked willingly for Maleficent, it can actually be interpreted as a "good thing."
Though their magic was stated to be secondary to Maleficent in raw power, they were capable of granting people extremely powerful weapons of righteousness, which could triumph over the darkest of evil, as seen when they gave Prince Phillip the Shield of Virtue and the Sword of Truth. In the final fight between Phillip and Maleficent (who had taken on the shape of a terrifying, fire-breathing dragon), they blessed Phillip's Sword of Truth with their magic, empowering it so that it could kill evil with one true, right, accurate blow.