For anyone who will ask about the cultist dungeon the puzzle is in the same room with the three flags, i was able to use the pillars in the room to change the colours of the flags, when i got them all yellow like the one at the big door chests appeared and not the opening of the doors area. i tried matching the other colours such as red, green and blue but it wont open. ill be trying deferent combinations going forth but can someone please tell me the answer.
*EDIT*
I found a switch in the room below the flag room, which can be found in the middle, in the only perfect square in the room.