The Painting puzzle (絵のパズル E no pazuru) is a puzzle in Version 6.23. It is in the hidden room, which is led from the stairs underneath the bathtub (located in the Annex Basement). It has 3 pictures on the wall and you have to use your Disc to find the color combination.
Solution[]
First, examine the Disc item and follow the arrow pointing clockwise. Follow the color combination of Red, Yellow, Yellow, Blue, Yellow, Red. Next, press the button on the first corresponding painting. Follow the color combination until the red painting falls off the wall. Collect the Metal Rod and combine it with the Disc to form the Hidden Door Key.