pixel_player90726877
Video: https://youtu.be/2EMdjiWQ6sI
I'm not 100% sure but I don't believe there is a blue stone.

Be careful how you interpret the information that the Langobard women give you.
"The Northern bridge to the woods is opened with the blue symbol."
[That's the color of placeholder]
"The Main bridge is opened with the beige stone."
[That's the color of the stone]
The color of the placeholder and the color of the stone are not always the same.