Here is a guide on how to unlock every scene in the Theatre. Hope it helps!
Cyan: Play the Storyline
Check with Mary in the evening after fully romancing her to have sex in the bath.
Complete Tana’s third mission to have sex with her.
Red: Sidequests
Bunny Girl: donate 10 goddess coins to the private chambers.
Maya: find all treasure map locations.
Fea: train intelligence and read all stone tablets.
Sera: complete all storage room puzzles.
Flora: collect her flowers and find all Gorgons.
Auri: solve the rift puzzle, drink her potion, return to her.
Lime: Postgame
Unlock these scenes by talking to the characters after finishing the story.
Orange: Halloween Horror
Unlock these scenes by finishing the Halloween Horror tale.
Pink: Salacious Sakura
Complete the Salacious Sakura tale to get the scenes with Mary, Roselyn and Minerva.
Find the hidden Charm in the crimson path for Akane’s scene.
White: Arctic Allure
Unlock these scenes by finishing the Arctic Allure tale.
Yellow: Bosom Beach
Unlock these scenes by finishing the Bosom Beach tale.
Blue: Gemstones
Deliver all gemstones to Nyx after finishing the story to unlock these scenes.
Black: Miscellaneous
Dark Elf: Enter the blue boundary, catch two guards “slacking off“ behind the breakable wall, talk to the guard on the left a few times.
Lederhosen Raylene: solve the second puzzle in Raylene’s cellar, grab the charm and craft the outfit.
Festive Mary: take Mary through the green boundary, go straight down, enter
the rift, open the chest next to the workshop, craft the outfit.
Cupid Roselyn: Complete the Lust Challenge in Roselyn’s storage, grab the charm and craft the outfit.
Here are all the Theatres guide for you, with this full guide, you won’t miss any theatre anymore.