From the Super Mario Wiki
A Vibe is an emotion forced on any living thing appearing in the game Super Princess Peach. In this title, Princess Peach is the main protagonist and can freely use one of four of types of Vibe: Rage, Gloom, Calm, and Joy. However, enemies continue using an infinite amount of a single type of Vibe until they are defeated, while Peach can only use Vibes until her Vibe Gauge is empty. As a mistake, the Calm heart has a happy face, and the Joy heart has a calm face.
 Vibe Gauge
The Vibe Gauge is the meter used to show the amount of Vibe energy that Peach currently has to use. The orange coloring shows the energy in the Vibe Gauge that is used for the Princess's Anger, Calm, Gloom, and Happy vibes, while blue coloring indicates that the Princess has no Vibe energy to use at all.