I've read as many posts as I could find about this topic and still having problems. I made it through dream world and understand the color combinations RGB/MYC and the vertices have to make up the color pattern on the medallion. I had found the medallion but left the world without knowing how to see the colors. Once I realized I needed the colors, I went back (clicked on a saved game) and was able to open the medallion and get the color sequence...... I have never started a new game but was wondering if going back to old saved games deletes or changes the game? Could this be why I can't get the marble code to open the door? Do I have to play all of Serenia over again??