Magical Metamorphosis

When the four magical girls activates their crystal charm with the power from their fabulous crystal, a magical metamorphosis. Used also in other franchises outside Forever! Starlight, a magical metamorphosis, a.k.a the magical dress up, is the moment when each of the four girls dress in their magical outfits, enhancing their powers.

Crystal Charms
Hikari,Ramona, Laetitia and Elodie all have crystal charms and fabulous crystals. More info here.

Changes compared to their civilian outfits
Aside their extravagant, princess-y outfits, a most prominent change is their hair color, who changes into a pastel tone (except for Laetitia, who have sparkles in her instead and a galaxy tone) and gets longer. Ramona and Laetitia have a different eye color (violet and indigo respectively).